IC-NRLF 


PRESETTED     TO    THE    LIBRARY 

OF     THE 

UNIVERSITY 

OF 

CALIFORNIA 


WITH    THE    COMPLEMENTS 
OF    THE 

PUBLISHER 


LABORATORY  MANUAL 


OF 


ELECTROTHERAPEUTICS 


BY 


WILLIAM  JAMES  HERDMAN,  Pn.  B.,  M.  D.. 

PROFESSOR  OF  DISEASES  OF  THE  NERVOUS  SYSTEM  AND  ELECT  R  Or 
THERAPEUTICS,  UNIVERSITY  OF  MICHIGAN. 


AND 

FRANK  W.  NAGLER,  B.S., 

INSTRUCTOR  IN  ELECTROTHERAPEUTICS 
UNIVERSITY  OF   MICHIGAN. 


GEORGE  WAHR,  PUBLISHER, 
ANN  ARBOR,  MICH. 


A- 


COPYRIGHT,    1898 
GEORGE  WAHR 


PREFACE. 

For  a  number  of  years  the  opportunity  has  been  given 
the  students  in  the  Department  of  Medicine  and  Surgery 
of  the  University  of  Michigan  to  learn  the  relation  which 
electricity  bears  to  physiological  action  and  the  rational 
application  of  that  action  to  therapeutics. 

For  some  years  attendance  upon  the  course  of  instruc- 
tion offered  in  this  branch  was  optional  with  the  student. 
But  so  great  has  been-the  accumulation  of  knowledge  con- 
cerning the  part  electricity  plays  in  the  movements  of  both 
animate  and  inanimate  things,  and  so  important  a  part  is 
it  found  to  take  in  determining  these  movements  that  it 
can  no  longer  be  excluded  from  a  curriculum  of  study  for 
medical  students  that  aims  to  be  thorough  and  complete. 

In  the  study  of  influences  which  affect  the  animal 
economy,  beneficially  or  otherwise,  it  is  quite  as  essential 
that  we  know  the  part  due  to  electric  action  as  to  know 
what  is  due  to  chemism  or  to  radiant  energy  in  the  form  of 
light  and  heat. 

It  has  been  our  experience  that  the  knowledge  required 
by  the  student  of  medicine  concerning  electricity  and  its 
relation  to  animal  economy  is  best  acquired  by  the  labora- 
tory method.  By  that  method  of  instruction  each  princi- 
ple is  impressed  upon  the  mind  through  several  separate 
paths  of  the  sense  perception  and  a  manual  dexterity  is 
acquired  which  is  essential  to  success  in  therapeutic  appli- 
cations. 

This  has  been  the  plan  adopted  for  teaching  electro- 
therapeutics at  the  University  of  Michigan.  Every  form 


i: 


ERRATA. 

Page  23  line  26  for  <4$S$"  read 
"     26     "     2  omit  "or". 

pr 
"     26     "    13  for  "C  —~^r      R"  write  C  = 


n        n  n 

1 '  in  ti  in   T 

"    26     "    18  for     —  R."    write =    R- 

n  n 

"  43     "    26  for  "experiment"  write  experimental. 

"  50  problem  27  insert  R  =.  2000. 

"  72  line  4  for  "floating"  write  placing. 

"  97     "     26  for  "no  direct"  write  no  volt  direct. 

"  102     "     4  for  "wire"  write  iron. 

"  105     "      13   for   "arrangements"  write  arrangement. 

"126    "     23  for  "from  the"  write  from  or. 


MEASUREMENT  OF  THE  DIRECT  CURRENT. 


The  Laboratory  Milliamperemeter. — The  ability 
to  understand  the  working  principles  and  to  use  intelli- 
gently some  form  of  galvanometer  is  absolutely  essential 
to  the  student  of  current  electricity.  A  very  simple  instru- 
ment in  the  hands  of  a  skillful  operator  can  be  made  to 

yield  comparatively  accurate  re- 
sults. The  instrument  used  in 
this  laboratory  (Fig.  i )  is  adapt- 
ed by  construction  to  carry  cur- 
rents which  are  best  expressed, 
as  thousandths  of  an  ampere  or 
"milliamperes;"  such  an  instru- 
ment is  called  a  milliampereme- 
ter.  This  laboratory  milliam- 
peremeter  consists  of  an  ordinary  compass  needle  mounted 
in  a  block  of  wood  with  the  wire  coils  beneath  the  needle. 
The  coils  are  wound  in  form  like  the  figure  8,  the  part 
between  the  binding  posts  being  straight  and  the  return, 
which  is  a  semi-circle  is  made  first  on  one  side  and  then 
on  the  other.  When  the  instrument  is  properly  placed  the 
the  straight  part  of  the  coil  lies  below  and  parallel  to  the 
magnetic  needle.  When  the  "A"  terminals  are  employed 
the  current  passes  eight  times  below  the  needle,  with  the 
"  B  "  terminals  it  passes  forty  times  below  it. 

The  fundamental  phenomenon  upon  which  the  con- 
struction of  this  galvanometer  form  of  milliamperemeter 
depends  is  as  follows; 


Fig    1. 


2  LABORATORY  MANUAL 

A  freely  suspended  magnetic  needle  tends  to  place  itself 
at  right  angles  to  a  wire  through  which  a  current  of  elec- 
tricity is  flowing. 

This  instrument  may  be  used: 

ist,    To  detect  the  presence  of  a  current; 

2d,     To  determine  the  direction  of  a  current; 

3d,     To  determine  strength  of  current; 

4th,   To  measure  electric  resistances; 

5th,  To  measure  and  compare  electro-motive  forces, 
etc. 

This  is  a  modified  tangent  galvanometer  and  for 
deflections  not  exceeding  10°  or  15°  the  currents  are 
nearly  proportional  to  the  deflection.  The  calibration  of 
one  of  these  instruments  gave  the  following  table  which 
shows  the  current  strength  in  milliamperes  corresponding 
to  a  given  deflection  both  for  the  A  and  B  terminals. 
This  table  may  be  used  for  all  instruments  of  this  particu- 
lar construction,  but  better  results  in  practical  work  are 
obtained  if  a  calibration  table  is  prepared  for  each  instru- 
ment. Each  galvanometer  should  be  carefully  examined 
to  see  whether  the  needle  swings  freely.  If  this  is  the 
case  it  will  come  to  rest  in  exactly  the  same  position  after 
every  deflection  if  the  instrument  has  not  been  moved. 

Throughout  the  following  experiments  in  which  elec- 
tric currents  are  to  be  measured,  or  compared,  it  will  be 
necessary  to  so  regulate  the  battery  power  as  to  keep  the 
deflection  within  the  limits  for  which  the  instrument  is 
calibrated. 


OF    ELECTROTHERAPEUTICS. 
GALVANOMETER    CALIBRATION    TABLE. 


CURRENT  IN 

CURRENT  IN 

CURRENT  IN 

w" 

MlLLIAMPERES. 

W 

W 

MA. 

in 

W 

MA. 

M 

W 

W 

erf 

0 

o 

O 

u 

Q 

A  Term. 

B  Term. 

w 
Q 

A  Term. 

B  Term. 

W 

Q 

A  Term. 

B  Term. 

jO 

i-5 

•25 

11° 

21.2 

5.65 

21° 

55-9 

14-94 

2° 

3- 

•52 

12° 

•23.8 

6.48 

22° 

61. 

15-95 

3° 

4-5 

•9 

13° 

26.5 

7-3 

23° 

67. 

16.97 

4° 

6-3 

1.32 

14° 

29.5 

8.2 

24° 

73-1 

18. 

5° 

8. 

1.8 

15° 

32.6 

9.08 

25° 

79-3 

6° 

10. 

2-3 

16° 

35-8 

10 

26° 

86.2 

7° 

12.  I 

2-9 

17° 

39-i 

10.9 

27° 

94. 

8° 

J4-3 

3-54 

18° 

42-7 

II.  "91 

28° 

102.2 

9° 

16.4 

4.2 

I9° 

46.8 

12.93 

29° 

110.8 

10° 

18.7 

4-9 

20° 

5L2 

13.93 

30° 

120.0 

Fig.  2.    The  Ordinary  form  of  Milliainperemeter. 


EXPERIMENTS  WITH   CURRENT  STRENGTH. 


The  Voltaic  or  Galvanic  Cell  (T.  168) — A  com- 
mon and  convenient  method  for  generating  a  current  of 
electricity  is  to  make  use  of  a  glass  or  porcelain  cup,  con- 
taining a  liquid,  as  acidulated  water,  in  which  two  pieces 
of  dissimilar  metals  are  partially  immersed.  If  to  the 
upper  extremities  of  these  strips  of  metal,  wires  are  at- 
tached and  the  opposite  ends  of  the  wires  are  connected 
to  the  binding  posts  of*  a  galvanometer,  the  deflection  of 
the  galvanometer  needle  will  give  evidence  that  a  current 
of  electricity  is  flowing  along  the  wires.  The  origin  of  the 
electricity  in  this  case  is  due  to  the  chemical  action  that  is 
taking  place  between  the  acidulated  water  and  one  of  the 
metal  strips,  and  is  at  the  expense  of  that  metal  since  it  is 
gradually  consumed.  This  is  a  transformation  of  chemi- 
cal energy  into  electrical  energy.  The  cup  and  contained 
liquid  and  metals  is  called  a  voltaic  or  galvanic  cell. 

EXPERIMENT  i. — Take  the  small  strips  of  copper  and 
zinc  furnished.     Attach  about  two  feet  of  copper  wire  to 
each  strip  and  attach  the  other  ends  of  the  wires  to  the  ter- 
minals of  the  galvanometer 
marked   B   in    fig.    3.     The 
most  sensitive  coil  of  the  gal- 
vanometer is  attached  to  the 

B  terminals,  and  for  this  reason  they  should  always  be  used 
in  measuring  or  testing  for  the  presence  of  weak  currents. 
Place  the  galvanometer  so  that  its  needle  shall  point  to  zero 
and  swing  clear  of  the  dial.  Immerse  the  strips  in  a  glass 
of  distilled  water,  being  careful  that  the  strips  do  not  touch, 
and  notice  whether  the  galvanometer  needle  is  deflected. 


OF    ELECTROTHERAPEUTICS.  5 

If  it  is,  it  indicates  that  a  current  of  electricity  has  been 
generated  and  that  there  is  a  difference  of  electric  poten- 
tial between  the  copper  and  zinc. 

EXPERIMENT  2. — Using  different  metals  and  a  glass  of 
hydrant  water  make  the  following  combination,  and  test  as 
in  the  preceding  experiment.  Note  the  deflection  given 
in  each  case  and  determine  which  combination  gives  the 
greatest  deflection,  in  other  words  the  strongest  current. 
The  connections  must  be  bright,  the  wires  tightly  fastened 
and  the  metal  strips  must  be  kept  the  same  distance  apart 
throughout  the  experiment.  It  will  be  found  convenient 
to  prepare  a  strip-holder  from  a  small  block  of  wood  and 
pieces  of  brass,  that  are  provided,  to  facilitate  the  fasten- 
ings of  the  plates  and  wires.  Tabulate  the  results  obtained 
as  follows: 


Def. 

Cu  —  C  

..     Def 

<  i 

"  Sn 

(( 

"  —  Fe 

tt 

tt 

"  Pb 

tt 

tt 

"      Brass 

(( 

ss  

tt 

«_Gal    Fe 

n 

.  Fe  .. 

« 

c^ 

"  —  Sn 
"-—  Fe 
"—  Pb 
"  —  Brass 


EXPERIMENT  3.  —  Repeat  the  preceding  experiment 
using  dilute  sulphuric  acid  (H2SO4)  (1:20)  and  common 
salt  (NaCl)  solution  as  exciting  liquids.  Use  the  A  termi- 
nals of  the  galvanometer  and  put  a  resistance  of  from  10 
to  25  ohms*  in  circuit.  Make  at  least  ten  more  combina- 
tions than  are  indicated  in  EXP.  2,  and  in  each  case  take 
three  readings. 

1.  First  swing  of  the  needle. 

2.  The  permanent  deflection. 

3.  The  permanent  deflection  after  three  minutes. 
*  These  resistances  will  be  found  on  the  side-  table. 


6  LABORATORY  MANUAL 

Note  in  each  case  which  metal  is  electropositive  (-J-) 
and  carefully  arrange  the  results  in  a  series  in  the  order  of 
the  greatest  first  swing  of  the  galvanometer  needle.  The 
order  of  the  metals  in  the  zinc  series  and  copper  series 
should  correspond.  It  will  be  found  convenient  always  to 
attach  the  zinc  to  the  north  and  copper  to  the  south  termi- 
nal of  the  galvanometer.  In  the  properly  arranged  series 
each  metal,  beginning  with  zinc,  will  be  electropositive  (4- ) 
with  respect  to  the  one  next  below  it. 

EXPERIMENT  4. — Into  some  dilute  sulphuric  acid 
(H2SO4)  ( i  :  20)  place  a  strip  of  commercial  zinc  (Zn)  and 
notice  the  result.  Collect  some  of  the  gas  given  off  in  a 
test  tube  and  determine  what  it  is.  What  would  you  ob- 
serve if  you  were  to  prepare  the  dilute  acid  ?  After  the 
liquid  has  become  clear  replace  the  commercial  zinc  by  a 
piece  of  chemically  pure  zinc  and  note  the  result  (T.  172). 
The  pure  zinc  should  be  carefully  polished  with  sand  paper 
to  remove  all  traces  of  foreign  metals  and  oxidation  on  its 
surface. 

EXPERIMENT  5. — Amalgamate  (see  page  21)  the  com- 
mercial zinc  (Zn)  (T.  174).  Notice  its  physical  changes 
and  try  to  bend  it  at  one  corner.  Immerse  it  again  in  the 
acidulated  water  and  compare  the  results  with  those  in 
EXP.  4. 

EXPERIMENT  6.  Place  a  strip  of  copper  in  the  dilute 
acid  and  notice  if  there  is  chemical  action  as  in  the  case 
of  the  zinc. 

EXPERIMENT  7. — Place  the  amalgamated  zinc  and 
copper  strips  in  dilute  acid,  being  careful  that  they  do  not 
touch  each  other.  How  do  the  results  compare  with  those 
in  EXP'S  5  and  6  (T.  173,  174)? 

EXPERIMENT  8. — Allow  the  metals  to  come  in  contact 
beneath  the  surface  of  the  liquid.  From  which  plate  does 


OF    ELECTROTHERAPEUTICS.  7 

the  gas  arise?  Is  it  the  same  as  in  EXP.  4?  Connect  the 
ends  projecting  above  the  liquid  by  a  wire.  Notice  that 
the  result  is  the  same  as  before.  Now  break  the  connec- 
tion, what  does  the  result  indicate?  With  the  wires  con- 
nected as  before  what  would  be  the  effect  of  putting  a  glass 
partition  in  the  retaining  vessel  between  the  two  plates? 
EXPERIMENT  9.  —  Connect  the  wires  to  the  A  terminals 
of  the  galvanometer  and  put  in  circuit  from  10  to  20  ohms 
resistance.  When  the  needle  rests  at  zero  immerse  the 
plates  in  the  fluid  and  take  the  reading.  Allow  the  cur- 
rent to  flow  5  minutes  and  note  the  deflection  every  half 
minute.  In  this  way  determine  what  combination  of  metals 
and  fluid  gives  the  strongest  and  most  uniform  current. 
Make  the  following  and  a  few  other  combinations: 

(  HNO    (1:20) 
(HSO.(i:io)*  r  or«  >         / 

Cu&Zn     CSOSol^  C&Zn     ^^Ld 

(NH.GlSol.  [NH4ClSol. 

Pb  and  Zn  with  H2SO4  (1:10)  and  others. 

EXPERIMENT  10. — Take  two  dissimilar  metals,  place 
one  above  the  tongue  and  the  other  beneath  it  and  then 
bring  the  ends  in  contact.  Observe  the  peculiar  sensa- 
tion. Try  several  combinations,  noticing  what  relation 
the  intensity  of  sensation  bears  to  the  deflection  of  the 
galvanometer  needle  obtained  with  the  same  pairs  of 
metals.  What  does  this  experiment  demonstrate? 

The  tongue  test  is  a  convenient  method  for  detecting 
weak  currents  and  for  currents  of  short  duration.  By 
practice  the  experimenter  can  approximately  estimate  elec- 
tro-motive forces  as  high  as  10  volts  without  danger  or 
discomfort.  The  student  should  also  familiarize  himself 

*  These  solutions  will  be  found  on  the  side  table.  Fill  the  glass  to 
the  depth  of  2  inches  in  each  case. 


LABORATORY  MANUAL 

with  the  difference  in  sensation  caused  by  the  positive  (-f-) 
and  negative  ( — )  terminals  and  thus  be  able  to  determine 
by  this  means  the  direction  in  which  a  current  is  flowing 
along  a  given  wire. 

EXPERIMENT  n. — Place  a  tumbler  containing  fresh 
bichromate  solution  fy  inch  deep  over  your  galvanometer 
dial.  In  this,  place  a  narrow  strip  of  amalgamated  zinc 
over  the  north-seeking  end  of  the  needle  and  a  carbon 
plate  over  the  south-seeking  end.  Touch  the  upper  ends 
of  the  strips  together  and  observe  the  needle.  It 
may  be  necessary  to  use  a  thin  glass  beaker  and  to  alter- 
nately open  and  close  the  circuit  to  get  a  noticeable  effect. 
What  relation  does  this  experiment  bear  to  the  preced- 
ing? What  do  the  two  experiments  prove  concerning  a 
battery  ? 

EXPERIMENT  12. — The  Volta  Pile.  —  Construct  a 
Volta  pile  (T.  164)  using  n  plates  each  of  copper  and 
zinc  separated  by  squares  of  blotting  paper  moistened 


Cu, 

-TTZ. 


j- 

Cit, 

Fig.  4. 

with  a  dilute  acetic  acid  solution.  (Strong  NaCl  solution 
or  any  weak  acid  solution  would  answer).  The  squares  of 
paper  should  be  just  the  size  of  the  plates  and  should  be 
moistened  before  setting  up  the  pile.  Arrange  the  plates  in 
the  order  indicated  by  the  diagram  (Fig.  4),  soldering  wires 
to  the  terminal  plates  and  fastening  the  whole  together  with 
a  rubber  band.  With  the  least  possible  delay  have  its 
voltage  measured  on  the  voltmeter,  being  careful  that  you 
have  made  the  proper  connection  before  closing  the  circuit 


6fr  ELECTROTHERAPEUTICS.  9 

through  the  instrument.  Bring  the  wires  into  contact  with 
your  tongue  and  compare  the  sensation  with  that  you 
experience  in  EXP.  10.  Attach  the  wires  to  the  A  termin- 
als of  the  galvanometer  with  a  resistance  the  same  as  you 
used  in  the  Zn,  Cu  and  NaCl  combination  and  compare 
results. 

The  volta  pile,  in  some  form,  has  been  called  upon 
to  do  duty  in  the  construction  of  that  innumerable  variety 
of  ' '  body  batteries  "  which  are  sold  under  the  names  of 
'•Electric  Belts,"  "Electric  Plasters,"  "Electric  Shoe 
Soles,"  etc.,  when  there  is  any  pretence  in  these  objection- 
able devices  to  generate  any  current  whatever,  for  often 
the  word  "  electric  "  is  simply  employed  as  a  catch-penny 
name  and  has  no  other  reason  for  its  application  to  the 
thing  so  named. 

Many  of  the  electric  belts  and  other  such  appliances 
are  capable  of  generating  a  current  of  considerable 
strength  so  that  when  used  by  those  ignorant  of  the  action 
of  electricity  or  of  the  proper  treatment  of  disease  by  it, 
they  seldom  do  good  and  often  do  great  harm. 

Soldering. — A  soldering  fluid  is  prepared  by  dissolv- 
ing scraps  of  zinc  in  hydrochloric  acid  (HC1)  till  no  more 
zinc  is  dissolved.  The  parts  to  be  united  must  be  scraped 
clean  and  bright,  and  care  must  be  taken  to  keep  them  so. 
Now  apply  some  of  the  soldering  fluid  to  the  surface  of 
the  metals,  place  a  small  piece  of  solder  between  them 
and  apply  heat  either  with  a  soldering  iron  or  by  holding 
the  parts  in  the  flame  of  a  Bunsen  burner,  being  careful  to 
remove  them  as  soon  as  the  solder  is  melted,  and  keep 
them  in  position  till  it  cools.  Should  the  solder  not 
spread  out  and  adhere  intimately  to  all  the  parts  the 
process  should  be  repeated. 


BATTERY  POLARIZATION. 

(T.  i75,  176.) 


Construct  a  Volta  cell  (T.  166),  using  plates  1^x3 
inches.  Use  the  same  plate  holder  that  you  used  in  EXP. 
2,  being  careful  that  the  metallic  parts  do  not  touch 
and  thus  "short  circuit"  the  cell.  Amalgamate  only  the 
the  lower  three-fourths  of  the  zinc  to  prevent  its  breaking, 
and  be  sure  that  all  metallic  connections  are  bright  and 
tight. 

EXPERIMENT  13. — Connect  the  terminals  of  your  cell 
to  the  A  terminals  of  the  galvanometer,  having  in  circuit  a 
resistance  of  at  least  10  ohms.  When  the  needle  comes  to 
rest  immerse  the  elements  in  the  dilute  acid.  Notice  that 
the  angle  of  deflection  diminishes  rapidly  for  a  time  and 
then  more  slowly.  Allow  the  cell  to  continue  in  action  for 
ten  minutes  and  then  jar  or  brush  the  gas  from  the  upper 
plate,  noticing  the  effect  on  the  needle.  Repeat,  keeping 
the  plates  constantly  in  motion.  In  each  case  take  the 
galvanometer  reading  every  half  minute  and  tabulate  the 
results. 

EXPERIMENT  14. — Replace  the  dilute  acid  of  EXP. 
13  by  bichromate  solution  (K2Cr2O7  +  H2  SO4  +  H2  O). 
Allow  the.  cell  to  continue  in  action  ten  minutes  and  then 
compare  the  deflections  of  the  needle  with  those  of  the 
preceding  experiment. 

EXPERIMENT  15. — Again  replace  the  bichromate  solu- 
tion of  EXP.  14  by  a  solution  of  copper  sulphate  (Cu  SO4). 
Allow  the  cell  to  act  ten  minutes,  take  half-minute  readings 
and  compare  them  with  those  of  EXP'S  13  and  14. 


OF   ELECTROTHERAPEUTICS.  II 

EXPERIMENT  16. — Attach  the  terminals  of  Volta's 
pile  to  the  A  terminals  of  the  galvanometer  and  let  the 
time,  resistance  and  observation  be  the  same  as  in  the  pre- 
ceding experiments.  Do  the  deflections  vary  ?  Why? 

The  Velio's  pile  should  be  taken  apart  and  the  plates 
cleaned  and  dried  as  soon  as  possible  after  using  it  to  avoid 
corrosion  of  the  plates. 

EXPERIMENT  17. — Examine  the  Daniell's  cell*  on  the 
side- table.  Test  it  as  to  its  polarization  in  the  same  way  as 
you  did  the  cells  in  the  preceding  experiments.  (T.  181). 

EXPERIMENT  18. — Test  Bunsen's  cell*  as  you  did  the 
Daniell's  and  examine  the  Grove's  cell.  (T.  182,  183). 

EXPERIMENT  19. — Determine  the  constancy  of  the 
Leclanch6  cell,  having  it  connected  up  for  ten  minutes. 
Record  the  readings  every  half  minute.  Now  allow  the 
cell  to  stand  on  open  circuit  for  a  minute  and  then  close 
the  circuit  only  long  enough  to  take  the  reading  the  instant 
the  needle  stops  oscillating.  Continue  this  for  ten  minutes 
keeping  the  circuit  closed  as  short  a  time  as  possible.  Do 
the  results  indicate  a  recovery  in  the  strength  of  current? 
If  so,  to  what  is  it  due?  (T.  184).  Because  of  the  time 
required  for  the  needle  to  come  to  rest  it  will  be  quite  as 
instructive  to  compare  the  first  swings  of  the  needle  in  the 
later  part  of  this  experiment. 

It  is  found  that  the  current  from  the  voltaic  cell  rap- 
idly diminishes  in  intensity,  so  that  in  a  short  time  the  ac- 
tivity of  the  cell  is  very  much  reduced  or  may  cease  alto- 
gether. This  may  be  due  to  several  causes,  the  chief  of 
which  is  the  collection  of  hydrogen  on  the  copper  plate, 
thus  causing  the  polarization  of  the  cell. 

From  Ohm's  law  (see  page  2 2), it  is  apparent  that  any- 

*  Note,  Specimens  of  these  cells  will  be  found  on  the  side  table. 


12  LABORATORY  MANUAL 

thing  which  tends  either  to  diminish  the  E.  M.  F.  or  to 
increase  the  resistance  of  a  cell  must  cause  a  diminution 
of  the  current  strength.  The  chief  effects  of  polarization 
are  the  following, — 

1.  The  presence  of  hydrogen  bubbles  on  the  copper 
plate  sets  up  an  E.  M.  F.  in  an  opposite  direction  to  the 
E.  M.  F.  acting  from  the  zinc  to  the  copper  plate.      The 
effective  E.  M.  F.  is  then  equal  to  the  difference  between 
the  two. 

2.  The  effective  surface   of  the  copper  plate  is  de- 
creased by  the  highly  resistant  hydrogen  gas,  and  then  the 
internal  resistance  of  the  cell  is  increased  and  the  current 
is  correspondingly  decreased. 

Methods  of  Preventing  Polarization.— i.  Any 
mechanical  method  of  removing  the  hydrogen  from  the 
negative  plate  such  as  brushing  the  plate  or  keeping  the 
liquid  of  the  cell  agitated  would  diminish  polarization. 
This  method  has  never  proved  to  be  very  satisfactory  and 
is  now  obsolete. 

2.  Polarization   may  be  prevented    by  surrounding 
the  negative  plate  of  the  cell  by  some  oxidizing  material 
which  is  capable  of  forming  a  chemical  combination  with 
the   nascent    hydrogen.      In    this    manner    the    two   chief 
causes  of  polarization  are  prevented.     Nitric  acid  (HNO3), 
chromic  acid  (CrO3),  manganese  dioxide  (Mn  O2)  and  Cal- 
cium hypochlorite  (Ca  (C1O)0)  are  commonly  employed. 

3.  By  placing  the  negative  plate  in  some  salt  whose 
metallic  element  can  easily  be  replaced  by  nascent  hydro- 
gen, polarization  can  be  entirely  prevented.     The  chem- 
istry  of    the    Daniell    and    Chloride    of    Silver    cells    will 
illustrate  this  principle. 


THE    ELECTRIC    BATTERY. 


An  electric  battery  is  composed  of  one  or  more  cells, 
each  cell  consisting  of  any  two  dissimilar  metals  placed  in 
a  liquid  capable  of  chemically  attacking  either  of  them. 
Any  combination  of  such  simple  cells  or  elements  is  called 
a  battery.  A  battery  composed  of  cells  is  still  one  of  the 
principal  sources  of  electricity  as  it  is  used  by  Physicians. 
One  of  the  simplest  forms  of  cells  for  such  a  battery  con- 
sists of  a  zinc  and  a  copper  plate  with  a  dilute  solution  of 
sulphuric  acid  for  exciting  liquid  and  is  known  as  the 
simple  voltaic  cell. 

The  generating  plate  is  the  name  given  the  zinc  or 
other  metal  attacked  by  the  liquid  because  part  at  least  of 
the  chemical  energy  expended  is  utilized  in  the  generation 
of  an  electric  current.  This  is  also  known  as  the  positive 
(-]-)  plate  and  it  invariably  diminishes  in  size  and  weight 
during  the  action  of  the  cell. 

The  collecting  plate  is  the  term  applied  to  the  cop- 
per, carbon,  platinum  or  other  metal  used  with  the  zinc. 
This  is  also  called  the  negative  ( — )  plate  and  it  should 
not  be  acted  upon  by  the  liquid  in  which  it  is  immersed. 

The  elements  consist  of  one  generating  and  one  col- 
lecting plate.  It  is  essential  that  the  exciting  liquid  should 
have  a  greater  chemical  affinity  for  the  former  than  for 
the  latter. 

The  poles  are  the  copper  strip,  from  which  the  cur- 
rent starts  in  the  external  circuit,  and  the  zinc  strip  toward 
which  the  current  flows.  These  are  known  as  the  positive 
(+)  and  negative  ( — )  poles  or  terminals  respectively. 


14  LABORATORY  MANUAL 

The  circuit  constitutes  the  entire  path  of  the  cur- 
rent. It  consists  of  an  internal  part  made  up  of  plates 
and  liquid  of  the  cell  and  an  external  part  composed  of 
the  connecting  wires  and  any  intervening  body  with  which 
they  may  be  in  contact. 

A  cell  is  on  short  circuit  when  its  terminals  are  con- 
nected by  a  short  wire  of  no  appreciable  resistance. 

A  cell  is  on  open  circuit  when  its  terminals  are  not 
connected  by  a  conductor  or  when  the  external  resistance 
is  infinitely  great. 


THE  CHEMICAL  REACTION   IN  VARIOUS 
BATTERIES. 


The  Simple  Voltaic  Cell.— This  cell  is  composed 
of  a  strip  of  zinc  and  one  of  copper  immersed  in  a 
dilute  solution  of  sulphuric  acid  (1:20  by  vol.).  During 
the  action  of  the  cell  the  zinc  is  attacked  by  the  acid,  but 
the  hydrogen  gas  thus  liberated  is  transferred  by  a  series 
of  molecular  interchanges  to  the  copper  strip  where  it 
can  first  be  seen. 

If  we  represent  the  arrangement  of  the  metals  in  the 
liquid  as  follows: 


Znx_z  |  ZnS04  |  H,SO4     H2  |  Cu. 

The  arrow  represents  the  direction  of  the  current 
through  the  cell.  The  zinc  and  the  hydrogen  are  dis- 
placed in  the  cUrection  of  the  current,  while  the  sulphion 


OF    ELECTROTHERAPEUTICS.  15 

or  SO4  part  of  the  acid,  is  displaced  in  the  other  direction. 
All  metals  and  hydrogen  are  electro  positive,  and  travel  in 
an  electrolyte  with  the  positive  current.  Zinc  sulphate  is 
formed  at  the  expense  of  zinc  and  sulphuric  acid,  and 
hydrogen  is  set  free  at  the  copper  plate.  The  simple 
chemical  action  taking  place  is,  the  displacement  of  the 
hydrogen  of  the  acid  by  zinc,  forming  zinc  sulphate 
instead  of  hydrogen  sulphate. 

The  electro-motive  force  (E.M.F.)of  this  cell  is  about 
i  volt  and  this  is  reduced   to   ^  volt  upon  polarization. 

The  Daniell  Cell. — This  cell  most  commonly  con- 
sists of  a  glass  vessel  containing  a  clear  solution  of  cop- 
per sulphate,  in  which  is  placed  a  cylinder  of  sheet  copper 
which  serves  as  the  negative  plate. 
Within    the    copper    cylinder    is 
placed  a  porous  cup  of  unglazed 
earthen  ware,  which  contains  the 
zinc  rod  immersed  in  dilute  sul- 
phuric acid  or  preferably  a  dilute 
solution  (5^)  of  zinc  sulphate. 

The  Gravity  Cell. — Is  a 
modified  form  of  the  Daniell,  in 
which  the  two  liquids  are  separ- 
ated only  by  their  difference  in 
density. 

If  we  represent  the  arrange- 
ment of  metal  plates  as  follows: 


Fig.  5.    Gravity  Cell. 


Znx    |  H2  So,  |  H2  SO4  ||  Cu  So4  |  Cu  SO4  |  Cu: 


then  after  the  first  interchange  it  becomes 

Znx_!  |  Zn  SO,  |  H3  SO4  ||  H8  SO4  |  Cu  SO,  |  Cuy+1 


1 6  LABORATORY  MANUAL 

It  will  be  seen  that  all  metallic  elements  and  hydrogen 
have  been  displaced  in  the  direction  of  the  current.  The 
zinc  has  lost  one  atom  while  the  copper  has  gained  one. 
One  molecule  of  zinc  sulphate  has  been  formed  and  one 
of  copper  sulphate  has  disappeared.  The  hydrogen  dis- 
places the  copper  in  Cu  SO4  and  never  reaches  the  copper 
plate.  Polarization  is  entirely  prevented  and  the  cell  is 

one  of  the  most  constant  known.      The  E.  M.  F.  is  1.08 
volts. 

The  Bu-nsen  Cell. — This,  like  the  Daniell,  is  a  two 
fluid  cell.  The  zinc  plate  bent  in  the  form  of  a  cylinder, 
is  generally  immersed  in  dilute  sulphuric  acid  contained  in 
a  glass  vessel.  A  cup  of  unglazed  earthenware  is  placed 
within  the  zinc  cylinder  and  contains  a  bar  of  carbon  im- 
mersed in  strong  nitric  acid.  The  hydrogen  formed  at  the 
zinc  plate  traverses  the  porous  cup,  but  then  decomposes 
the  nitric  acid  with  the  formation  of  a  corresponding 
amount  of  water.  The  electric  chain  may  be  represented 
as  follows: 

Znx      H2  SO,  |  H2  SO4  ||  2H  NO3— HNO3  |  C 

After  the  first  step  in  the  chemical  reaction  this 
becomes — 

Znx_i  |  Zn  SO4  |  H2  SO4  ||  2HNO3     HNO2  |  H2O     C 

It  will  be  seen  that  the  nitric  acid  has  been  reduced 
to  nitrous  acid  (HNO2),  which  in  turn  may  lose  an  atom 
of  oxygen,  becoming  hypo-nitrous  acid  (HNO).  Or  further, 
the  nitric  acid  may  be  broken  up  completely,  according  to 
the  following  reaction:  — 


OF    ELECTROTHERAPEUTICS. 


The  nitric  oxide  gas  (NO)  thus  formed  on  escaping 
from  the  liquid  immediately  combines  with  oxygen  of  the 
air,  forming  the  red  and  very  corrosive  fumes  of  nitrogen 
peroxide  (NO2).  This  cell  is  capable  of  furnishing  a  very 
strong  current,  but  the  generation  of  corrosive  fumes  and 
the  fact  that  it  requires  attention  at  frequent  intervals 
cause  it  to  be  much  less  used  than  other  forms  of  cells. 
The  E.  M.  F.  is  1.8  volts. 

The  Bichromate  Cell.— The  elements  in  this  cell 
are  zinc  and  carbon  plates  immersed 
in  a  fluid  composed  of  bichromate  of 
potassium,  (or  chromic  acid),  sulphuric 
acid  and  water. 

When  a  solution  of  potassium  bichro- 
mate is  treated  with  sulphuric  acid,  a 
purely  chemical  reaction  takes  place, 
resulting  in  the  formation  of  chromic 
acid.  Thus:  — 

K2  Cr2  07+H2  S04= 

K2S04+H2  0+2  Cr  08. 

Fig.6.  Bichromate  cell.  The  chromic  acid,  Cr  O3,  is  the  use- 
ful agent  to  effect  depolarization  by  the  oxidation  of  hydro- 
gen. The  process  is  supposed  to  be  represented  in  the 
following  reaction: — 

,6  H+2Cr  03+3H2  S04=6  H2  O+Cr2  (SO,)3. 

The  final  result  is,  therefore,  the  production  of  the 
sulphate  of  zinc  (at  the  positive  plate),  the  sulphates  of  po- 
tassium and  chromium,  and  water. 

The  cell  should  be  so  constructed  that  both  the  zinc 
and  carbon  plates  can  be  removed  from  the  liquid  when 

not  in  use.     The  E.  M.  F.  is  two  volts. 
? 


l8  LABORATORY  MANUAL 

Battery  Fluid. — The  following  formulae  are  gener- 
ally employed  in  the  preparation  of  the  battery  fluid: 

No.   i.     Sulphuric  acid  (commercial) 3  fluid  oz. 

Potassium  bichromate  (powdered) 2  oz. 

Water 16  fluid  oz. 

*(Bisulphate  of  mercury 2  drachms. 

First  dissolve  the  bisulphate  of  mercury  and  then  the  potassium 
bichromate  in  the  water,  and  then  slowly  add  the  sulphuric  acid  with 
constant  stirring.  Allow  the  liquid  to  cool  before  using. 

No.  2.     Chromic  acid  (Cr  O3) 2  oz. 

Water 16  fluid  oz. 

Sulphuric  acid [^    "       " 

(Bisulphate  of  mercury 2  drachms.) 

This  fluid  is  much  to  be  preferred  to  the  former,  since  the 
absence  of  potassium  salts  prevents  the  formation  of  chrome  alum, 
K2Cr2(SO4)4,  which  is  very  difficult  of  removal  from  the  bottom  of  the 
battery  jar. 


Fig.  7.    A  Series  of  Bichromate  Cells. 

The  Leclanche'  Cell. — This  form  of  cell  is  prob- 
ably more  used  by  physicians  than  all  other  forms  taken 

*NOTE. — The  bisulphate  of  mercury  must  never  be  placed  in  the 
battery  fluid,  except  when  carbon  is  used  as  the  negative  plate. 


OF   ELECTROTHERAPEUTICS. 


collectively.     The  little  attention  required,  the  ease  with 

which    it    can    be 

restored     and    the 

cheapness     are    all 

factors  which   have 

brought  it  into  such 

general    use.      The 

elements    are    zinc 

and  carbon  and  the 
|  exciting  liquid   is  a 

strong    solution    of 

ammonium    chlor- 

Pig.  8.  Leianchs  Cell.  i  d  e.  Depolarizers 
are  sometimes  employed.  When  manganese  dioxide 
(MnO0)  is  used  as  a  depolarizer  it  is  packed  about  the 
carbon  plate  and  the  arrangement  may  be  represented  as 
follows: 


Fig  9    Carbon 
depo1 


Zn 


2  MnO2  |  C. 


which  becomes 

Znx_z  |  Zn  C12  |  2NH4C1  ||  2NH. 


Mn203 


HO  I  C. 


As  a  result  of  evaporation  the  double  chloride  of  zinc 
and  ammonium  is  liable  to  crystallize  on  the  zinc  and  on 
the  bottom  of  the  glass  jar.  This  should  be  prevented 
as  far  as  possible  since  it  produces  a  deleterious  eifect. 
Owing  to  oxidation  and  local  action  the  zinc  rod  is  often 
entirely  severed  at  the  surface  of  the  liquid.  This  is  one  of 
the  first  signs  of  disorder  in  the  cell  and  can  be  almost  indef- 
initely postponed  by  protecting  the  zinc  where  it  passes 
through  the  surface  of  the  liquid  by  a  thin  coat  of  pararHne. 
This  cell  is  well  adapted  to  open  circuit  work.  Its  E.  M, 


2O  LABORATORY  MANUAL 

F.  varies  from  1.4  to  1.7  volts,  but  in  a  short  time  polar- 
ization may  reduce  it  to  .7  volt  from  which  it  slowly 
recovers.  The  tops  of  the  battery  jar  and  the  carbon 
plate  are  placed  in  melted  paraffine  and  if  on 
setting  up  the  cell,  these  parts  are  not  moist- 
ened by  the  battery  fluid,  disagreeable  "creep- 
ing "  of  the  salts  will  be  prevented. 

The  Chloride  of  Silver  Cell.— The  ele- 
ments in  this  cell  are  zinc  and  silver  and  on 
the  latter  is  fused  the  silver  chloride  which  is 
readily  reduced  by  nascent  hydrogen  and  thus 
Fig.  10.  serves  as  a  depolarizer.  The  exciting  liquid 
may  be  ammonium  chloride  and  in  this  case  the  chemical 
reaction  may  be  represented  as  follows: 

Znx  |  2NH4C1  |  2NH4C1  |  2AgCl  |  Agy. 
After  the  first  interchange  this  becomes 

Znx_,  |  ZnCl2  |  2  NH4C1  |  2NH4C1  |-Agy+a. 

Polarization  is  prevented  in  a  manner  analagous  to 
that  in  the  Daniell  cell.  Because  of  its  small  size  this 
cell  adapts  itself  admirably  to  the  construction  of  port- 
able batteries  for  physicians  use.  It  should  never  be  used 
to  send  anything  but  small  currents  as  the  materials  would 
otherwise  quickly  become  exhausted.  The  E.  M.  F.  is 
about  1. 1  volts. 

NOTES  ON  THE  ACTION  OF  BATTERIES. 

1.  In  all  cells  in  which  acid  is  used   as  the  exciting 
liquid  the  zinc  must  be  amalgamated.      In  other  types  of 
cells  amalgamation  of  the  zinc  is  not  accompanied  by  any 
deleterious  effects. 

2.  During  the  action  of  a  cell  no  effervescence  of 
gas  should  occur  at  the  zinc   plate,      Such  phenomena 


OF    ELECTROTHERAPEUTICS.  21 

indicate  that  the  zinc  should  be  more  thoroughly  amal- 
gamated. 

3.  In  batteries  employing  porous  cups  the  fluid  about 
the  mcorrodable  plate  should  never  be  higher  (nor  in  fact 
quite  as  high)   as  the   fluid  about   the  zincs.      This  will 
diminish  one  form  of  local   action  by  delaying  the  diifu- 
sion  of  the  oxidizing  fluid  toward  the  zinc  plates. 

4.  Most  batteries  should  have  their  plates  removed 
from   the   liquid  immediately  after  they  have  been  used. 
In  two  fluid  cells  the  liquids  should  also   be  put  in  their 
respective  labeled  bottles. 

5.  Detached  carbon  plates  can  be  resoldered  to  their 
attachments  after  a  thin  layer  of  copper  has  been  depos- 
ited upon  one  end  by  electrolysis.     (This  process  will  be 
more  fully  treated  under  the  subject  of  electrolysis). 

METHODS  OF  AMALGAMATING    ZINC. 

Any  expenditure  of  chemical  energy  within  a  cell 
which  does  not  contribute  to  the  production  of  an  electric 
current  is  designated  as  local  action.  Such  action  may  take 
place  either  upon  closed  circuit  or  upon  open  circuit. 
Such  wasteful  chemical  actions  are  most  often  due  to  the 
local  electric  circuits  formed  between  commercial  zinc 
and  its  impurities.  It  is  almost  entirely  prevented  if  the 
surface  of  the  zinc  is  covered  by  an  alloy  of  mercury  and 
zinc,  which  is  known  as  an  amalgam. 

The  zinc  plate  may  be  amalgamated  in  the  following 
ways: 

1.  Clean  the  zinc  in   dilute  acid  and  rub   mercury 
over  its  surface  with  a  small  cloth.      The  mercury  spreads 
readily  if  the  zinc  surface  is  properly  cleaned. 

2.  An  amalgamating  fluid  is   prepared  by  dissolving 
mercury  in  aqua  regia  (three  parts  of  hydrochloric  acid  to 


22  LABORATORY  MANtJAL 

one  of  nitric  acid)  and  then  adding  a  small  excess  of 
hydrochloric  acid.  If  zinc  be  dipped  into  this  solution 
for  a  few  moments  its  surfaces  will  receive  a  deposit  of 
metallic  mercury. 

3.  A  soluble  salt  of   mercury  is  sometimes  dissolved 
in  the  battery  fluid  to  keep  the  zinc  amalgamated. 

4.  An  alloy  of  zinc  and  mercury  is  sometimes  pre- 
pared for  the  positive  plate.      Such  plates  seldom  need  be 
removed  for  amalgamating,  but  since  they  are  much  more 
brittle  greater  care  must   be   exercised   in  handling  them. 

NOTE. — All  forms  of  jewelry,  such  as  rings,  chains,  etc.,  are  liable 
to  injury  by  amalgamation  and  should  consequently  be  removed  before 
working  with  mercury. 


OHM'S  LAW  AND  THE  ELECTRIC  UNITS. 


In  order  to  understand  this  most  important  law  of 
voltaic  electricity  it  is  first  necessary  to  sharply  distinguish 
between  the  three  following  electrical  quantities: 

1.  The    Current  (C)  is  the  quantity  of  electricity 
which  flows  past  any  point  in  a  circuit   in   one   second. 
The  unit  of  current  strength  is  called  the  Ampere. 

2.  Electro-motive  force   (E.  M.  F.)  or  (E)  may 
be  denned   as  that  which  causes  electricity  to  move  from 
one  point  to  another.      It  is  sometimes  spoken  of  as  elec- 
tric pressure.      The  unit   of  eletro-motive  force  is  called 
the  Volt. 

3.  Resistance  (R)  refers  to  that  which  impedes  or 
checks  the  flow  of  electricity  over  a  conductor.      It  is  the 
inverse  of  conductance.     The  unit  of  resistance  is  called 
the  Ohm. 

Ohm's  law  may  be  expressed  as  follows:  The  current 
which  flows  in  a  circuit  varies  directly  as  the  electro -motive 
force,  and  inversely  as  the  resistance. 


OF  ELECTROTHERAPEUTICS.  23 

This  relation  may  be  expressed  as 

E 
=  R 

when  C,  E  and  R  represent  respectively  the  units  of  cur- 
rent, electro-motive  force  and  resistance.  From  the  above 

•p> 
relation  it  is  evident  that  E  =  CR  and  R   =  —  . 

V-x 

It  follows  that  if  any  two  of  the  three  quantities  be  given 
the  third  can  be  derived  by  calculation. 

[The  following  are  among  the  units  adopted  by  the 
Electrical  Congress  held  in  Chicago  in  1*893.  They  are 
designated  International  Units  to  distinguish  them  from 
definitions  previously  adopted. 

The  International  Ohm  is  represented  by  the  resis- 
tance oifered  to  an  unvarying  electric  current  by  a  column 
of  pure  mercury  at  the  temperature  of  melting  ice,  14.4521 
grammes  in  mass,  of  a  constant  cross-sectional  area  and 
of  the  length  of  106.3  centimeters. 

The  International  Ampere  is  represented  by  the  un- 
varying electric  current  which  deposits  silver  from  a  solu- 
tion of  silver  nitrate  in  water  at  the  rate  of  .001118 
grammes  per  second.  The  solution  must  be  of  a  definite 
strength,  and  the  whole  process  must  be  according  to  cer- 
tain specifications. 

The  International  Volt  is  that  electromotive  force 
which,  acting  through  a  resistance  of  one  ohm,  will  pro- 
duce a  current  of  one  ampere.  It  is  represented  suffi- 
ciently well  by  TiHHy  of  the  electromotive  force  of  a  Clark's 
standard  cell  at  15°  C.] 


u 


METHODS  OF  JOINING  CELLS. 

A.  In  Series. — In  this  method  the  cells  are  con- 
-T?=*>     f~*~\     r*~r^     r~"~\     r^~  nested  so  that  the  posi- 

|    |      |    |       |    |       !_J         tive  pole  of  one  joins  the 
Fig.  11.  negative  of  the  next  and 

so  on  throughout  the  entire  number  of  cells. 

B.  In  Multiple  Arc. — In  this  arrangement  the  cells 
are  so  joined  that  the  pos- 
itive   poles    are    all   con_ 

nected   together   to  form 
a  common    positive  pole 

Fig.  12. 

on  one  side,  the  negative 

poles  being  also  joined  together  to  form  a  common  neg- 
ative pole  on  the  other  side  (T.  168). 

C.  In  Combination. — Partly  in  series  and   partly 
in  multiple  arc.      In  this  arrangement  groups  of  cells  con- 
nected in  series   are  there  joined 
in  multiple   arc  as  if  each  group 
were  a  single  cell. 

The    group    in    the    diagram 
would  be  spoken  of    as  three  in 
series  and  three  in  multiple  arc, 
involving    nine    cells,   while  five 
Fig.  13.  in  series    and    eight    in    multiple 

arc  would  require  forty  cells,  etc. 

OHM'S  LAW  APPLIED   TO  CELLS    IN  SERIES. 


inn/i 

KTTLT 
TJUTT 


Ohm's  law    being  expressed  by  c  =-~-  *s    true 

R 

when  R  represents  the  sum  of  all  the  resistances  in  circuit 


OF  ELECTROTHERAPEUTICS.  25 

and  when  E  represents  the  algebraic  sum  of  all  the  elec- 
tro-motive force.  If  E  =  the  E.  M.  F.  of  a  cell  and  r  = 
its  internal  resistance,  then  the  current  sent  through  a 
given  external  resistance  (R)  will  be  represented  by 

C-     E 

~ 


If  m  represents  any  number  of  cells  joined  in  series  it 
follows,  since  both  E  and  r  increase  with  m,  that  the  cur- 

rent will  be  represented  by  C  =  -  ~  • 

m  /*-{-  -K 

When  the  external  resistance  or  (R)  —  o  or  when  it  is  so 

small  as  to  be  negligible  C  =  —  —  -   =   —    it   is  evident 

mi  -\-  o          r 

that  m   cells   furnish  no  stronger  current  than  one  alone. 
When  on  the  other  hand  R  is  a  large  quantity  as  com- 

pared to  m  r,  C  =  —  —  —  and    the    current   is    therefore   m 
times  as  great  as  that  from  one  cell. 

OHM'S  LAW  APPLIED  TO  CELLS  IN  MULTIPLE. 

When  r  equals  the  resistance  of  a   single  cell  and  we 
have  n  such  cells  joined  in  parallel,  the   total  resistance 

becomes  —  .      The   E.  M.  F.  of  n  cells  in  multiple   is  no 
n 

greater  than  for  a  single  cell,  Ohm's  law  therefore  becomes 

E  »E 


C  = 


:-+* 


It  follows   that  when  the  external  resistance  or  (R) 
=  o  the  current  is  n  times  as  great  as  for  a  single  cell,  since 

C  =  —• 


26  .     LABORATORY  MANUAL 

When,  however,  R  is  a  large  quantity  the  formula  is 
approximately  true  or  when  written  C  =  —  =-  in  which 
case  n  cells  furnish  no  stronger  current  than  a  single  cell. 

OHM'S  LAW  APPLIED  TO  A  MIXED  CIRCUIT. 
(A  combination  of  cells  in  series  and  multiple  arc.)  Fig.  i%. 
If  m  is  the  number  of  cells  in  series  and  n  the  number 
in   multiple  arc  then  the  whole  number  of  cells  —  m  n. 
From  preceding   articles   it  follows   that  the  resistance  of 
m  cells  in  series  =  m  r  and  if  in  n  such  groups  be  joined 
in  multiple  arc  the  entire  internal  resistance  will  become 

--     Since  the  E.  M.  F.  is  only  affected  by  the  number 

n 

of  cells  in  series,  Ohm's  law  becomes: 

E          E 


c  =  - 


mr_    ,    R        r        R 
n     r  m       n        m 

From  this  formula  the  following  rule  can  be  mathe- 
matically derived,  viz.  A  given  battery  will  send  the 
greatest  current  through  an  external  resistance  when  it  is 
so  connected  that  the  internal  and  external  resistance  are 

equal.      Or  when  —   -  =  R. 


CONSTRUCTION  OF  EXPERIMENTAL  BATTERY. 


An  eight  cell  battery  is  now  to  be  constructed  from 
the  materials  furnished.  The  wooden  frame  for  holding 
the  battery  jars  and  plates  is  furnished  and  should  be  fitted 
up  with  the  plates,  wires,  binding-posts,  a  device  for  rais- 
ing and  lowering  the  plates,  etc.  Contact  is  made  with  the 
zinc  plates  by  soldering  bare  copper  wires  8  c.m.  in  length 
to  them.  Similar  wires  are  to  be  soldered  to  eight  pieces 
of  sheet  copper  i  by  1.5  c.m. 
which  can  be  wedged  in  con- 
tact with  thecarbon  plates  thus 
making  the  contact  with  them. 
For  a  more  permanent  form  of 
battery  it  would  be  advisable 
to  deposit  first  a  thin  layer  of 
copper  upon  one  end  of  each 
of  the  carbon  plates  by  elec- 
trolysis and  then  solder  di- 
rectly to  the  carbon  plate.  In 

order  that  the  battery  when  joined  in  series  may  yield  the 
required  E.  M.  F.,  (16  volts),  all  contacts  must  be  clean  and 
tight,  and  all  local  action  prevented  by  thorough  amal- 
gamation of  the  zinc  plates. 

EXPERIMENTS    WITH     THE     BATTERY. 

EXPERIMENT  20. — The  galvanometer  may  be  used  to 
determine  the  polarity  of  wires  coming  from  a  battery  or 
other  generator  of  an  elrctric  current,  thus  indicating  the 
direction  of  the  current  (T.  197).  Connect  the  terminals 
of  the  Volta  cell  to  the  B  terminals — the  long  coil  of  the 


Fig.  14.    Experimental  Battery. 


2 8  LABORATORY  MANUAL 

galvanometer — and  notice  the  direction  in  which  the  needle 
is  deflected.  Now  reverse  the  poles  and  observe  that  the 
deflection  is  in  the  opposite  direction.  After  having  once 
determined  the  deflection  for  a  current  of  known  direc- 
tion, you  can  easily  determine  the  polarity  or  direction  of 
current  in  a  wire  when  the  generator  is  not  visible.  The 
importance  of  chis  matter  cannot  be  well  over-estimated, 
since  in  practice  it  is  absolutely  essential  to  know  the 
direction  of  current  when  passed  through  the  body. 

EXPERIMENT  21. — Let  the  student  opposite  you  ar- 
range wires  coming  from  a  hidden  cell  that  you  may  test  the 
polarity  with  the  galvanometer.  Determine  the  polarity 
of  the  terminals  marked  X  and  Y,  over  the  side-table  which 
are  in  connection  with  a  cell  in  the  dispensing  room.  Note 
accurately  the  time  when  the  test  was  made. 

EXPERIMENT  22. — Pass  the  current  from  a  cell  by 
means  of  an  insulated  wiie,  directly  over  and  parallel  to 
the  galvanometer  needle.  The  wire  can  be  wound  around 
the  A  terminals  to  hold  it  in  position.  Now  bend  the  wire 
leading  from  the  cell  to  the  galvanometer  so  that  it  also 
lies  nearly  parallel  to  the  needles.  Why  does  this  affect 
the  deflection  ?  Bring  a  magnet  or  a  piece  of  iron  near 
the  needle  while  the  current  is  flowing  and  notice  that  the 
deflection  is  changed. 

EXPERIMENT  23.  —  The  E.  M.  F.  of  a  cell  is  independ- 
ent of  the  size  of  the  cell.  Prove  by  placing,  in  circuit 
with  your  galvanometer,  a  resistance  of  200  ohms,  using 
the  A  terminals  or  a  still  larger  resist- 
~+~  ance  with  the  B  terminals.  The  latter 
would  be  the  better  method  in  com- 
paring the  electro-motive  forces  of  different  cells.  Prepare 
a  little  cell  (Fig.  15)  by  hollowing  out  a  piece  of  carbon 
so  it  will  hold  a  drop  of  bichromate  fluid,  thus  making 


OF    ELECTROTHERAPEUTICS.  2Q 

the  carbon  serve  the  double  purpose  of  negative  element 
and  battery  jar.  The  positive  element  should  be  a  small 
pointed  piece  of  zinc,  which  is  to  be  dipped  into  the  drop 
of  liquid  when  the  circuit  is  to  be  completed.  Pass  the  cur- 
rent successively  from  a  large  bichromate  cell, — one  cell  of 
your  experimental  battery — and  the  small  cell  just  prepared, 
through  the  galvanometer.  Do  you  get  the  same  deflection 
in  each  of  the  these  cases-?  What  do  the  results  indicate  ? 

EXPERIMENT  24. — With  the  galvanometer  and  resist- 
ance as  in  the  previous  experiment,  connect  one  cell  of  the 
experimental  battery  with  a  large  bichromate  cell  so  that 
the  current  from  one  shall  oppose  that  of  the  other. 
Finally  join  the  large  cell  in  opposition  to  the  little  cell  of 
EXP.  23.  In  both  cases  observe  the  needle  and  account 
for  the  results. 

EXPERIMENT  25. — Without  changing  the  galvanome- 
ter or  resistance,  connect  one  of  the  bichromate  with  a 
voltaic  cell  so  that  their  currents  shall  tend  to  oppose. 
Why  does  the  galvanometer  needle  move  in  this  case  and 
not  in  the  other?  What  is  the  logical  conclusion,  and 
what  is  the  direction  of  the  current  in  this  experiment  ? 

EXPERIMENT  26.  —  The  E.  M.  F.  is  independent  of  the 
depth  of  fluid  in  the  cell.  Prove  by  leaving  in  circuit  your 
galvanometer  and  a  resistance  of  at  least  200  ohms,  take 
the  galvanometer  reading  and  then  gradually  raise  the 
plates  from  the  liquid.  Observe  that  the  deflection  does 
not  change  until  the  plates  leave  the  liquid.  Why  do  you 
use  a  high  resistance  in  this  experiment  ? 

EXPERIMENT  27.  —  The  E.  M.  F.  of  a  number  of  cells, 
in  series,  is  equal  to  the  sum  of  the  electro-motive  forces  of 
the  several  cells.  Prove  by  putting  in  circuit  with  your 
galvanometer,  A  terminals,  a  resistance  of  200  ohms  and 
then  pass  the  current  from  first  one  cell  then  two,  three, 


LABORATORY  MANUAL 


etc.,  till  the  entire  eight  of  the  experimental  battery  are  in 
circuit.  Take  the  galvanometer  reading  as  each  cell  is 
introduced  and  tabulate  results,  writing  the  current  strength 
opposite  each  deflection.  •  Can  you  explain  the  results  ? 
(T.  212,  fig.  121 ). 

EXPERIMENT  28.  —  The  E.  M.  F.  of  a  number  of  cells 
in  multiple  arc  is  the  same  as  that  of  one  cell.  Prove  this 
by  having  the  galvanometer  and  resistance  as  in  the  pre- 
ceding experiment,  placing  first  one  cell  in  circuit  then 
adding  the  remaining  cells  one  at  a  time  in  multiple  arc. 
Take  the  galvanometer  reading  at  each  addition  and  ob- 
serve that  the  results  throughout  agree  with  the  above 
statement.  Do  you  think  it  necessary  to  have  so  much 
resistance  in  circuit  ? 

EXPERIMENT  29.  —  The  E.  M.  F.  of  a  battery  com- 
posed of  x  cells  in  series  and  y  cells  in  multiple  arc  the 
number  of  cells  being  xy )  is  equal  to  x 
times  the  E.  M.  F.  of  one  cell.  Having 
galvanometer  and  resistance  arranged 
as  in  the  past  experiments,  prove  by 
joining  the  cells  in  groups,  of  two  in 
series  then  joining  the  groups,  one  at 
a  time,  in  multiple  arc,  each  time  tak- 
ing the  galvanometer  reading.  It  will 
not  be  found  difficult  to  verify  the 
above  statement  by  the  arrangement  of 
the  cells. 

EXPERIMENT  30. — When  groups  of 
cells  are  coupled  against  each  other  the 
available  E.  M.  F.  is  the  difference 
Fig.  16.  Water  Rheostat,  between  the  electro-motive  forces  of 
the  opposing  groups.  Having  in  circuit  a  resistance  of  200 
ohms  and  the  galvanometer,  A  terminals,  couple  two  cells 


OF    ELECTROTHERAPEUTICS.  31 

of  the  experimental  battery  in  series,  and  take  the  read- 
ing. Now  replace  the  two  cells  by  the  entire  eight  of  the 
battery  so  joined  that  three  of  the  cells  shall  oppose  the 
other  five.  Does  the  needle  indicate  the  same  E.  M.  F. 
in  both  cases  ?  Other  combinations  may  be  made  to  prove 
the  statement. 

EXPERIMENT  31. — No  current  of  electricity  can  flow 
except  in  a  closed  circuit,  and  the  current  is  of  the  same 
strength  at  all  points  in  the  circuit.  Prove  this  by  connect- 
ing the  entire  battery  in  series  with  four  resistances  vary- 
ing from  10  to  600  ohms.  Now  introduce  the  galvanome- 
ter in  the  circuit  between  any  two  cells  or  resistances  or 
between  the  battery  and  a  resistance,  and  notice  that  the 
needle  indicates  the  same  current  in  each  case. 

EXPERIMENT  32. — Having  one  cell  of  the  experi- 
mental battery  send  the  current  through  the  galvanometer 
and  take  the  reading.  Now  introduce  in  succession  the 
following  resistances  25,  60,  TOO,  150,  200  and  600  ohms. 
In  the  last  case  use  the  B  terminals  also.  In  each  case 
take  the  deflection  and  by  reference  to  the  calibration 
table  find  the  strength  of  current.  Also  calculate  the  cur- 
rent in  each  case  by  Ohm's  law,  and  compare  results.  The 
r  of  a  cell  may  be  called  4  ohms. 
What  are  the  sources  of  error  ? 

EXPERIMENT  33.— Use  the  A  ter- 
minals of  the  galvanometer  to  meas- 
ure the  current  given  by  i,  2,  3,  4 
cells  suc-cessively,  coupling  the  cells 
in  series.  Why  do'  4  cells  give  no 

Fig.  17.    Graphite  Rhostat. 

greater  current  than  one  ?     Calculate 

the  strength  of  current  in  each  case.  The  resistance  of 
the  galvanometer  coil  connected  with  the  A  terminals  is 
about  one-tenth  of  an  ohm. 


32  LABORATORY  MANUAL 

EXPERIMENT  34. — Repeat  EXP.  33,  using  a  resistance 
of  from  100  to  200  ohms.  Why  does  the  current  increase 
as  the  cells  are  added?  Calculate  the  current  by  Ohm's 
law  as  before. 

EXPERIMENT  35. — Again  repeat  EXP.  33,  but  this  time 
coupling  the  cells  in  multiple  arc  instead  of  in  series.  Why 
do  you  get  a  greater  current  from  four  cells  than  from  one 
in  this  case  ?  Again  express  the  strength  of  current  by 
Ohm's  law. 

EXPERIMENT  36. — With  the  A  terminal  of  the  galvan- 
ometer and  a  resistance  of  200  ohms,  measure  in  succes- 
sion the  current  from  i,  2,  3  and  4  cells  in  multiple  arc. 
Why  do  the  four  give  no  greater  current  than  one? 

To  measure  the  internal  resistance  of  a  cell  join 
two  cells  of  the  experimental  battery  in  opposition  and  then 
send  the  current  from  a  large  bichromate  cell  through 
them,  having  the  galvanometer  in  circuit.  Note  carefully 
the  deflection  of  the  galvanometer.  Now  remove  the  two 
cells  joined  in  opposition  and  introduce  in  their  place  a 
known  resistance  such  as  will  make  the  deflection  exactly 
equal  to  the  former  reading.  The  current  being  the  same 
in  the  two  cases,  it  is  evident  that  the  resistance  introduced 
equals  that  of  the  two  cells  of  the  experimental  battery. 
This  conclusion  is  only  allowable  in  case  the  E.  M.  F. 

throughout  the  experi- 
ment is  kept  constant, 

C  //  ~lL  If  "|L  If  ix  ,J  and  care  must  be  taken 

that  the  E.  M.  F.  of 
Fig.  is.  the  cell  does  not  fall 

because  of  polarization.  It  is  advisable  to  repeat  this  ex- 
periment, joining  two  other  cells  of  the  experimental  bat- 
tery in  opposition  and  then  average  the  results. 

EXPERIAIENT  37. — Having  the  experimental   battery 


OF    ELECTROTHERAPEUTICS.  33 

joined  in  series,  pass  the  current  through  a  glass  of  dis- 
tilled water,  using  the  B  terminals  of  the  galvanometer. 
Now  add  enough  salt  to  the  water  to  make  a  i  per  cent, 
solution.  Calculate  the  resistance  of  the  water  in  both 
cases,  letting  the  wires  be  immersed  one  inch  and  keeping 
them  one  inch  apart.  Two  per  cent,  and  other  solutions 
may  also  be  measured. 

EXPERIMENT  38. — Using  from  four  to  eight  cells  of 
the  experimental  battery,  determine  by  calculation  from 
Ohm's  law,  the  resistance  of  the  various  parts  of  the 
body,  being  careful  in  regions  about  the  head  and  neck  that 
the  current  is  barely  strong  enough  to  give  a  good  reading 
on  the  galvanometer.  The  electrodes  should  be  carefully 
covered  with  absorbent  cotton  and  moistened  in  a  solution 
of  common  salt  or  ammonium  chloride.  In  no  case  should 
the  metallic  portion  of  an  electrode  be  bronght  in  eontact  with 
any  part  of  the  body  except  when  local  electrolytic  effects  are 
desired. 

Determine  the  resistance  through  the  following: —  • 

1.  From  one  hand  to  the  other; 

2.  From  the  hand  to  the  elbow; 

3.  From  elbow  to  the  back  of  the  neck; 

4.  Laterally  through  the  neck; 

5.  From  back  of  the  neck  to  the  temple; 

6.  Through  the  temples; 

7.  Through  the  hand; 

8.  Through  the  muscular  part  of  the  forearm. 

Determine  the  difference  in  effect  when  large  elec- 
trodes are  used  instead  of  small  ones.  (Difference  in  cur- 
rent density.  See  pg.  38.) 

EXPERIMENT  39. — Measure  the  unknown  resistance  at 
i,  2,  3,  4  and  5  on  block  A  or  B,  C,  D,  E,  F,  etc.,  by 
calculation  from  Ohm's  law,  using,  when  possible,  only 


34  LABORATORY  MANUAL 

sufficient  battery  power  to  give  a  deflection  not  much  ex- 
ceeding 10°.  For  large  resistance  the  B  terminals  will  give 
the  best  results,  but  in  this  case  the  resistance  of  the  gal- 
vanometer must  be  considered  in  the  calculation. 

EXPERIMENT  40. — Resistance  may  be  measured  by 
substitution.  In  this  method  the  resistance  to  be  meas- 
ured is  placed  in  circuit  and  the  galvanometer  reading 
taken.  The  unknown  resistance  is  then  removed  from  the 
circuit  and  in  its  place  a  known  resistance  is  substituted 
which  will  give  exactly  the  same  deflection  as  did  the  un- 
known. The  two  resistances  are  then  equal — 

(1)  in  case  you  succeeded  in  getting  exactly  the  same 
deflection  in  both  cases,   and 

(2)  if  the  E.  M.  F.  of  the  battery  has  not  varied  dur- 
ing the  experiment. 

Measure  the  R  of  two  blocks  of  "unknowns,"  and 
report  the  results  to  the  instructor  in  charge. 


DIVIDED  CIRCUITS  (T.  409). 


If  the  poles  of  a  battery  be  connected  by  two  or  more 
conducting  paths,  the  current  will  divide,  each  path  carry- 
ing a  definite  portion  of  the  whole  current.  The  principal 
laws  relating  to  divided  circuits  and  joint  resistances  are 
the  following: 

1.  The  sum  of  the  currents  in  the  several  branches 
is  equal  to  the  main  current. 

2.  Each  branch  will  carry  such   a  proportion  of  the 
whole  current  as  its  conductivity  bears  to  the  conductivi- 
ties of  all  the  branches.     The  conductivity  of  any  path  is 
the  reciprocal  of  its   resistance.      If  the   resistance   =  R 

the  conductivity  =  —  • 

Jx 


OF    ELECTROTHERAPEUTICS. 


35 


3.  The  total  conductivity  of  a  number  of  branches 
of  a  divided  circuit  is  equal  to  the  sum  of  the  conductiv- 
ities of  the  several  branhes. 

4.  The  joint  resistance  of  any  number  of  branches 

in  divided  circuit  is  less 
than  the  resistance  offered 
by  any  branch  taken  se- 
parately. 

EXPERIMENT  41. — Put 
in  circuit  with  your  gal- 
vanometer (A  terminals) 
a  R  of  200  ohms  and  use 
four  cells  in  series.  Note 
the  deflection.  Without 
interrupting  the  current 
join  the  battery  terminals 
with  three  feet  of  German  silver  wire,  number  30  to  36,  and 
note  the  effect  on  the  deflection.  The  wire  is  a  "  shunt" 
and  forms  one  branch  of  a  divided  circuit.  Now  replace 
the  German  silver  wire  by  a  short  piece  of  copper  wire 
and  notice  that  the  deflection  decreases  still  more.  Why? 
EXPERIMENT  42. — With  the  same  terminals  of  the 
galvanometer,  but  using  only 
one  cell,  connect  the  term- 
inals by  two  wires  which 
have  a  R  of  25  and  100 
ohms  respectively.  Now, 
introduce  the  galvanometer 
first  into  one  circuit  and  Fig.  20. 

then  the  other  and  observe  the  deflections.  From  your 
results  what  relation  can  you  deduce  between  the  cur- 
rent strength  and  the  resistances  of  the  branches?  Write 
out  the  ratio  between  the  two  currents. 


36  LABORATORY  MANUAL 

EXPERIMENT  43. — Using  but  one  cell,  put  in  circuit 
your  galvanometer  and  a  R  of  50  ohms.  Take  the  read- 
ing. Now,  in  the  same  part  of  the  circuit  and  between  the 
galvanometer  and  battery,  place  a  shunt  having  a  R  of  50 
ohms.  Take  the  reading  and  then  introduce  a  second 
shunt  having  a  R  of  100  ohms  beside  the  first.  Notice 
as  each  resistance  is  introduced  the  needle  indicates  an 
increase  of  current.  Why? 

Take  the  reading  in  milliamperes  and  then  remove  the 
galvanometer  from  the  position  in  the  main  circuit  closing 

the  circuit  where  it  was  re- 
moved.  Place  it  in  turn  in 
each  branch  of  the  divided 
circuit,  being  careful  to  keep 
the  circuit  closed  in  all  the 
.  21.  branches.  In  each  case, re- 

gister the  current  in  milliamperes.  Determine  whether 
the  sum  of  the  currents  in  the  shunts  equals  that  in  the 
main  wire.  Make  a  complete  diagram  showing  the  posi- 
tion of  each  part  in  every  case. 

EXPERIMENT  44. — Use  one  of  the  boards  arranged 
with  a  divided  circuit.  Place  the  galvanometer  in  the 
main  circuit. 

1.  Determine  by  substitution  each  of  the  six  resist- 
ances. 

2.  From   the   values  obtained  in  one,  calculate  the 
joint  resistance  of  the  six. 

3.  Determine  the  joint  resistance   of  the  six  by  the 
substitution  method. 

4.  From   data   thus   far  at  hand  calculate  what  per 
cent,  of  the  whole  current  will  flow  in  each  branch. 

5.  Determine  experimentally,  using  one  or  possibly 
two  cells,  the  whole  current  flowing  in  the  six  part  shunt. 


OF    ELECTROTHERAPEUTICS. 


37 


6.  Determine  experimentally  the  strength  of  current 
in  each  branch  and  what  per  cent,  of  the  whole  current 
it  is. 

Prepare  a  table  showing  how  your  calculated  and 
experimental  results  agree. 

The  Shunt  Method  of  Controlling  Currents.— 
When  any  E.  M.  F.  acts  through  a  circuit  it  is  found  that 
there  is  a  gradual  fall  of 
potential  from  one  part  of 
the  circuit  to  another.  In 
fact  it  can  be  easily  demon- 
strated experimentally,  that 
the  fall  of  potential  between 
any  two  points  in  the  circuit 
is  proportional  to  the  resist- 
"ance  between  them.  If  we 
let  R  =  whole  resistance  of 


Fig.  22.    Diagram  of  Graphite  Shunt 
Rheostat.    See  pg.  35. 


the  circuit.  R'=  resistance 
between  any  two  points  of 
the  circuit.  PD  =  whole  potential  difference;  then  the 
difference  of  potential  P'D'  over  the  resistance  of  R'  will 
be  determined  by  the  following  proportion: 

PD  :  P'D'  ::  R  :R' 

It  is   evident  from    this  that  by  varying  the  value  of  R', 
P'D'  will  be  correspondingly  changed. 

This  principle  readily  adapts  itself  to  the  regulation 
of  currents  for  therapeutic  uses,  especially  the  commercial 
currents  which  cannot  be  well  regulated  by  the  use  of  re- 
sistance alone.  Several  forms  of  current  controllers  and 
rheostats  employing  this  principle  are  on  the  market,  and 
their  efficiency  in  permitting  a  gradual  increase  of  current 
through  the  patient  and  then  of  again  gradually  reducing 


38  LABORATORY  MANUAL 

it  to  zero  before  removing  the  electrodes  is  certainly  such 
as  to  recommend  them  to  a  more  extended  use. 

It  is,  perhaps,  necessary  to  say,  that  such  instruments 
may  be  used  to  control  all  forms  of  current  electricty  ap- 
plied directly  to  the  body,  the  resistance  in  this  case  being 


Fig.  23.    Shunt  Controller  for  Dynamo  uuncu to. 

comparatively  great.  They  are  not  so  readily  adapted  to 
control  the  stronger  currents  required  by  the  cautery  or 
exploring  lamp. 

CURRENT    DENSITY. 

Current  density  may  be  denned  as  the  quantity  of 
current  per  unit  surface  of  the  electrode.  Thus  a  current 
of  i  milliampere  entering  the  body  from  an  electrode 


OF     ELECTROTHERAPEUTICS.  39 

whose  active  surface  is  i  square  centimeter,  may  be  tem- 
porarily considered  as  the  unit  of  current  density  in  elec- 
tro-therapeutics. Consequently,  in  the  application  of  a 
given  current  to  the  body,  the  density  of  the  current  varies 
inversely  with  the  active  surface  of  the  electrode  employed. 
Except  in  such  cases  when  the  destructive  electrolytic  ac- 
tion of  the  current  is  desired  it  is  necessary  to  cover  a 
metallic  electrode  with  some  moist  conducting  material 
and  so  place  it  upon  the  skin  that  the  current  shall  flow 
uniformly  through  all  parts  of  the  electrode. 


ELECTROLYSIS. 


The  process  of  separating  a  compound  chemical  sub- 
stance into  its  constituents  by  pasing  an  electric  current 
through  it  is  called  electrolysis.  The  substance  thus 
decomposed  is  called  an  electrolyte.  The  electrolyte  is 
always  decomposed  into  at  least  two  simple  products 
called  "ions."  The  plate  or  surface  at  which  the  cur- 
rent enters  the  electrolyte  is  called  the  anode,  that  by 
which  the  current  leaves  being  called  the  cathode.  •  The 
"ions"  collecting  at  the  anode  are  anions,  while  those  at 
the  cathode  are  cathions. 

The  quantity  of  the  electrolyte  decomposed  is  directly 
proportioned  to  the  quantity  of  electricity  passed  through 
it — that  is,  to  the  current  multiplied  by  the  time — and  the 
decomposition  takes  place  at  the  same  rate  at  all  parts  of 
the  circuit.  A  direct  current  is  accurately  measured  by 
determining  experimentally  the  rate  at  which  it  effects  elec- 
trolysis. Thus  the  ampere  is  that  current  which  will 
deposit  on  the  cathode  ,001118  grams  of  silver  per  second 
from  a  solution  of  a  silver  salt.  The  same  current  will 


4O  LABORATORY  MANUAL 

decompose  a  grain  of  water  in  twelve  minutes  or  will 
deposit  A  of  a  grain  of  copper  from  CuSO4  per  minute. 

An  ion  instead  of  remaining  free  may  combine  either 
with  the  electrode  or  with  the  electrolyte,  forming  a  sec- 
ondary product.  In  general,  in  the  electrolysis  of  the 
salts  of  the  alkali-metals,  caustic  alkali  and  hydrogen 
appear  at  the  cathode  while  free  acid  and  oxygen  appear 
at  the  anode.  Salts  of  the  heavy  metals  usually  give  a 
deposit  of  that  metal  at  the  cathode  and  a  free  acid  and 
oxygen  at  the  anode.  (T.  235). 

In  performing  the  following  experiments  perfect  clean- 
liness is  necessary  as  slight  traces  of  acid  on  the  fingers  or 
table  may  interfere  with  the  results  of  the  experiment. 

EXPERIMENT  45. — Attach  platinum  electrodes  to  the 
poles  of  the  experimental  battery  and  have  the  galvanom- 
eter, B  terminals,  in  circuit.  Immerse  the  platinum  of  the 
electrodes  in  a  glass  of  distilled  water.  Observe  the 
strength  of  current  and  see  whether  you  can  observe  any 
traces  of  decomposition  of  the  water.  Now,  add  a  few 
drops  of  strong  H2SO4  and  notice  the  changes  that  take 
place  in  the  fluid. 

In  this  and  the  following  experiments  where  chemical 
changes  are  involved  write  formula  showing  the  nature  of 
the  changes. 


•••••••••••BHHMMBSer 

Fig.  24.    Uterine  Electrodes  for  Electrolysis. 

EXPERIMENT  46. — Electrolize  a  solution  of  CuSO4 
first  using  platinum  and  then  copper  electrodes.  Employ 
two  cells  of  your  battery  and  measure  the  current  in  each 


OF    ELECTROTHERAPEUTICS.  41 

case.  The  electrodes  should  be  of  the  same  size  and 
should  be  kept  at  the  same  distance  apart  throughout  the 
experiment.  How  do  you  account  for  the  variation  of 
the  current  in  the  two  cases?  Try  the  experiment  with 
only  one  cell.  (T.  487). 

EXPERIMENT  47.  —  Electrolize  a  solution  of  CuSO4 
using  platinum  electrodes.  Notice  the  deposit  of  copper 
on  the  cathode.  This  illustrates  electro-plating,  other 
metals  being  deposited  from  solutions  of  their  salts  in  a 
similar  manner.  Hydrogen  and  the  metals  travel  with  the 
current  and  are  found  on  the  cathode  while  oxygen  and 
the  non-metals  always  collect  at  the  anode.  Determine 
by  this  method  the  polarity  of  the  terminals  x  and  y  on 
the  side-table. 

EXPERIMENT  48. — You  can  prove  that  the  copper  of 
the  anode  is  dissolved  by  using  the  copper  covered  plati- 
num as  anode  in  the  electrolysis.  In  a  short  time  the 
copper  will  have  disappeared.  Tarnished  copper  will 
become  bright  by  being  worn  away  at  the  anode  while  the 
cathode  increases  in  weight  from  the  depositing  of  copper 
upon  it.  Dissolve  the  copper  deposit  on  the  platinum  by 
dipping  the  latter  in  strong  HNO3  found  on  the  side-table. 

EXPERIMENT  49. — Electrolize  a  solution  of  sodium 
sulphate  (Na2SO4)  using  platinum  electrodes.  What  gases 
are  liberated  ?  Is  there  a  decomposition  of  the  salt?  Are 
the  gases  primary  or  secondary  products  of  decomposi- 
tion? Make  yourself  familiar  with  the  various  chemical 
changes  taking  place  and  write  the  chemical  equations. 

EXPERIMENT  50. — Place  some  neutral  Na2SO4  solution 
colored  with  litmus  in  a  V  tube  and  pass  the  current 
through  the  electrolyte  a  few  minutes,  using  platinum  elec- 
trodes. Notice  the  evolution  of  gases  as  before,  also 
that  the  solution  becomes  blue  about  the  cathode  and  red 


42  LABORATORY  MANUAL 

about  the  anode  indicating  the  formation  of  free  acid  and 
free  alkali. 

EXPERIMENT  51. — Having  your  hands  clean  and  of 
perfectly  neutral  reaction,  lay  a  piece  of  blue  litmus  paper 
on  the  palm  and  a  red  piece  on  the  back  of  the  hand. 
Wet  both  pieces  with  a  neutral  solution  of  Na2SO4,  press 
clean  copper  electrodes  against  them  and  allow  the  current 
to  flow  from  the  palm  to  the  back  of  the  hand.  Use  8 
cells  of  your  battery  and  allow  the  current,  which  is  quite 
weak,  to  flow  for  about  10  minutes.  Notice  that  the 
papers  have  changed  color. 

EXPERIMENT  52.  — Repeat  EXP.  51,  but  this  time  care- 
fully cover  the  electrodes  with  absorbent  cotton  moistened 
with  the  neutral  Na2SO4  solution.  If  the  experiment  is 
properly  performed  the  litmus  paper  on  the  hand  will  not 
change  color,  but  a  piece  in  contact  with  the  metal  of  the 
electrodes  will  change  color.  The  strength  of  current 
being  weak  you  should  allow  it  to  flow  long  enough  to  give 
marked  results. 

This  experiment  shows  the  value  of  covered  elec- 
trodes and  suggests  the  rule: 

When  using  the  galvanic  or  direct  current,  never  place 
bare  or  non-porous  electrodes  in  contact  with  the  skin  or 
mucous  membranes  unless  you  wish  to  obtain  at  the  points  of 
contact  the  effect  of  free  acid  or  free  alkali. 

EXPERIMENT  53. — Electrolize  a  solution  of  NaCl, 
using  carbon  electrodes.  Notice  the  odor  of  free  chlorine. 
Now,  use  iron  electrodes  and  notice  that  less  chlorine  is 
given  off,  but  that  the  anode  is  being  corroded,  giving  a 
light  colored  solution  of  iron  salt  near  the  anode.  Finally 
the  alkali  liberated  at  the  cathode  will  pass  over  by  dif- 
fusion and  cause  a  precipitate  of  ferrous  and  ferric 
hydrates.  Iron  salts  cause  more  or  less  discoloration  of 


OF    ELECTROTHERAPEUTICS. 


43 


the  tissues  in  which  they  are  set  free.  For  this  reason  in 
minor  surgical  operations  such  as  the  removal  of  superflu- 
ous hairs,  moles,  warts,  etc.,  especially  on  the  exposed 

parts  of  the  body,  the 
cathode  rather  than  the 
anode  should  be  em- 
ployed. 

EXPERIMENT  54.— 
Electrolize  a  solution 
of  Na2SO4  using  pla- 
tinum electrodes  and 
a  simple  voltaic  cell. 
Place  the  galvano- 
meter, B  terminals,  in 
j^^H^^-^^j^^^  circuit  and  have  the 

Fig.  25.    Chloride  of  Silver  Battery.  electrodes    in    position 

before  closing  the  circuit  by  placing  the  battery  plates  in 
the  liquid.  Upon  closing  the  circuit  observe  the  galvano- 
meter needle  and  explain  why  it  returns  to  zero  so  quickly. 
(T.  487).  Now  use  one  of  your  bichromate  cells  in  a 
similar  manner  and  explain  the  difference  in  behavior. 

EXPERIMENT  55. — Polarized  electrodes  constitute  an 
independent  source  of  E.  M.  F.,  which  acts  in  an  oppo- 
site direction  to  that  of  the  electrolizing  current.  This 
can  be  shown  in  the  following  manner.  Place  in  circuit 
with  your  galvanometer  the  entire  experiment  battery 
coupled  in  series  and  a  pair  of  clean  copper  electrodes 
between  which  is  a  layer  of  absorbent  cotton  wet  with  a 
neutral  solution  of  Na^C^.  Allow  the  current  to  flow  a 
few  minutes,  observe  the  deflection  and  then  break  the 
circuit  by  raising  the  battery  plates.  Wait  till  the  needle 
comes  to  rest  and  then  connect  the  wires  attached  to  the 
battery  terminals,  thus  making  a  circuit  including  only 


44  LABORATORY  MANUAL 

the  electrodes  and  galvanometer.      Notice  the  amount  and 
direction  of  the  deflection. 

EXPERIMENT  56. — Remove  a  few  hairs  from  the  back 
of  your  hand  by  electrolysis,  using  a  fine  sewing  needle 
as  the  electrode.  The  anode,  which  should  be  of  medium 
size  and  covered  with  absorbent  cotton  soaked  with  a 
saline  solution,  may  be  placed  upon  any  convenient  sur- 
face, as  on  the  muscular  part  of  the  forearm  or  the  palm 
of  the  hand.  Introduce  the  needle  along  a  hair  into  the 
hair  follicle,  have  the  galvanometer,  B  terminals,  and  bat- 
tery in  circuit  and  then  complete  the  circuit  by  placing 


Fig.  26.    Needle  Holder  for  Electrolysis. 

the  anode  in  position.  The  person  operated  on  can  be 
taught  to  vary  the  strength  of  current  both  by  pressure 
upon  the  electrode  and  by  varying  the  amount  of  surface 
in  contact  with  the  anode.  If  properly  done  a  little  froth 
will  appear  around  the  needle  and  the  hair  will  come  out 
easily.  Determine  what  was  the  greatest  strength  of  cur- 
rent during  the  operation.  Try  the  effect  of  having  all 
parts  in  position  and  then  suddenly  turning  on  the  current 
by  immersing  the  battery  plates.  Which  do  you  consider 
the  better  method? 

In  the  actual  electro-therapeutic  practice,  some  form 
of  graduated  rheostat  or  controller  should  be  em- 
ployed so  as  to  permit  the  gradual  entrance  and  with- 
drawal of  the  current  when  the  circuit  is  completed,  with 
the  patient  forming  a  part  of  it.  By  this  means  all  unpleas- 
ant shocks  are  avoided. 

EXPERIMENT  57. — It  is  often  necessary  in  electrolytic 
work  that  only  a  limited  portion  of  the  tissue  should  be 


OF     ELECTROTHERAPEUTICS.  45 

exposed  to  the  action  of  the  current  or  that  the  skin  should 
be  protected  from  the  caustic  products  at  the  point  of 
insertion  of  the  electrodes.  In  such  cases  all  but  the  tips 
of  the  needles  can  be  insulated  by  dipping  them  into  alco- 
holic shellac,  protecting  the  tips  by  small  pieces  of  cork. 
Dry  over  a  gas  burner  heating  enough  to  drive  off  all 
traces  of  alcohol  and  secure  an  even  coating  over  the  sur- 
face. In  removing  a  growth,  requiring  the  insertion  of  both 
electrodes,  it  will  be  found  that  the  anode  cannot  be  easily 
withdrawn.  If  the  current  be  reversed  for  a  short  time 
the  tissue  about  the  electrode  will  soften  and  it  can  then 
be  removed  without  injury  to  the  tissues. 

EXPERIMENT  58. — Electrolize  a  piece  of  fresh  meat 
which  retains  its  juices,  employing  steel  needles  as  elec- 
trodes. Observe  and  describe  the  effect  at  the  point  of 


Fig.  27.    Dispert-ing  Electrode. 

insertion  of  both  the  anode  and  cathode  needles.  Insert- 
ing each  needle  one  inch  and  keeping  them  one  inch 
apart,  determine  the  resistance  in  ohms  of  the  fresh  tissue 
between  them. 

EXPERIMENT  59. — Take  4  glasses  out  of  your  exper- 
imental battery  and  wash  them  clean,  then  fill  each  half 
full  with  a  neutral  Na2SO4  solution  containing  a  little  alco- 
holic solution  of  phenol-phthalein,  and  arrange  them  in  a 
row.  Connect  the  remaining  four  cells  of  your  battery  in 
series  and  connect  the  wires  of  this  battery  to  the  end 
glasses  containing  the  phenol-phthalein  so  that  the  wires 


46 


LABORATORY  MANUAL 


dip  into  the  fluid  at  the  sides  of  the  glasses.  Complete 
the  circuit  through  the  remaining  glasses  by  short  pieces 
of  copper  wire,  allowing  the  fluid  in  each  glass  to  form  as 
wide  an  interval  in  the  circuit  as  possible.  Measure  the 
strength  of  current  passing  and  also  note  the  change  of 
color  in  the  cells  throughout  the  row  after  the  current  has 
passed  for  a  few  minutes.  Phenol-phthalein  is  a  delicate 
test  for  the  presence  of  an  alkali.  Why  should  this  elec- 
trolytic change  take  place  in  the  middle  glasses  with  which 
the  terminal  wires  are  not  in  contact?  Is  the  amount  of 
chemical  action  the  same  in  each  of  the  four  electrolytic 
cells? 


. 


Fig.  '28.    Universal  Connectors. 

Laws  of  Resistance. — In  the  solution  of  the  prob- 
lems here  given,  the  following  brief  summary  of  the  laws 
of  resistance  should  be  borne  in  mind: 

1.  The  resistance  of  conductors  of  the  same  mate- 
rial and  thickness  varies  directly  as  the  length. 

2.  The  resistance  of  conductors  of  a  given  material 
and   length   varies   inversely  as   the  area  of  cross  section. 
Areas  of  circles  are   proportional   to  the  square  of  their 
diameters. 

3.  The  resistance   of  a   wire  of  a  given  length   and 
diameter  depends  upon  the  material  of  which  it  is  made — 
that  is,  upon  the  specific  resistance  of  the  material. 


PROBLEMS. 

The  following  problems  are  given  with  the  view  of 
putting  into  practice  the  facts  and  principles  that  have 
been  treated  of  in  the  preceding  experiments.  To  these 
others  will  be  added  when  needed  for  the  purpose  of  illus- 
trating or  emphasizing  certain  rules  or  facts  that  may  not 
seem  to  be  fully  grasped  by  the  student. 

PROBLEM  i. — A  certain  battery  whose  r  is  .5  ohms 
gives  a  current  of  i  ampere  through  a  R  of  4  ohms. 
What  is  its  E.  M.  F.  ? 

PROBLEM  2. — A  battery  of  40  cells  each  having  an  r 
of  .4  ohms  is  arranged  8  in  series  and  5  in  multiple  arc. 
If  the  current  flowing  through  a  wire  of  no  appreciable  re- 
sistance is  31.2  amperes,  what  must  be  the  E.  M.  F.  of  each 
cell  ?  What  is  the  strength  of  current  through  each  cell  ? 

PROBLEM  3. — Twenty  cells  in  multiple  arc,  each  hav- 
ing SL  r  of  30  ohms,  send  a  current  of  J-  ampere  through 
an  external  resistance  of  1.5  ohms.  What  is  the  E.  M.  F. 
of  each  cell  ? 

PROBLEM  4.  — Find  the  current  flowing  through  a  cir- 
cuit composed  of  a  galvanometer  having  a  R  of  100  ohms, 
a  battery  which  has  an  E.  M.  F.  of  6  volts,  and  having  a  r 
of  .8  ohms,  and  connecting  wires  with  a  R  of  5  ohms. 

PROBLEM  5. — The  E.  M.  F.  of  a  cell  is  r.8  volts  and 
its  r  .06  ohms.  Would  5  of  these  cells  in  series  light  an 
incandescent  lamp  which  has  a  R  of  10  ohms,  and  which 
requires  .8  amperes  of  current?  How  many  milliamperes 
of  current  are  furnished  ? 

PROBLEM  6. — Five  cells,  each  having  an  E.  M.  F.  of 


48  LABORATORY  MANUAL 

2.5  volts,  and  a  r  of  .2  ohms  are  joined  first  in  series  and 
then  in  multiple  arc.  Find  the  difference  in  the  strength 
of  current  if  the  R  of  the  conducting  wires  is  practically 
zero. 

PROBLEM  7.  Find  the  current  from  24  cells  arranged 
6  in  series  and  4  in  multiple  arc  if  the  E.  M.  F.  of  each 
cell  is  i  volt  and  the  r  of  each  cell  3  ohms,  the  R  being  45 
ohms. 

PROBLEM  8. — Take  15  cells,  each  having  an  E.  M.  F. 
of  1.5  volts  and  a.  r  of  .2  ohms.  What  would  be  the  cur- 
rent strength  if  three  of  the  cells  were  joined  in  opposition 
to  the  other  twelve  ? 

PROBLEM  9. — A  battery  whose  E.  M.  F.  is  6  volts  and 
whose  r  is  2  ohms  sends  a  current  of  1400  milliamperes. 
What  must  be  the  resistance  offered  in  the  circuit  ? 

PROBLEM  10. — A  battery  of  5  cells  in  series,  each  cell 
having  an  E.  M.  F.  of  2  volts,  produces  2  amperes  of  cur- 
rent when  the  external  resistance  (R)  is  3  ohms.  What  is 
the  r  of  each  cell  ? 

PROBLEM  n. — The  E.  M.  F.  of  a  cell  is  i  volt,  its 
internal  resistance  (r)  2  ohms.  How  many  such  cells 
joined  in  series  will  be  necessary  to  send  a  current  of  55 
milliamperes  through  an  external  resistance  of  890  ohms? 

PROBLEM  12. — If  the  r  of  a  cell  is  i  ohm  and  you 
have  90  such  cells,  how  should  they  be  connected  so  as  to 
send  the  strongest  current  through  an  external  resistance 
of  10  ohms  ? 

PROBLEM  13. — If  the  E.  M.  F.  of  a  cell  is  2  volts, 
and  its  internal  resistance  4  ohms,  what  would  be  the  least 
number  of  such  cells  required  to  send  a  current  of  i  am- 
pere through  an  external  circuit  offering  a  resistance  of  15 
ohms? 

PROBLEM  14. — What  is  the  best  way  to  connect  12 


OF    ELECTROTHERAPEUTICS.  49 

cells,  each  having  an  E.  M.  F.  of  i  volt  and  an  internal 
resistance  of  3  ohms,  in  order  to  send  the  maximum  cur- 
rent through  an  external  resistance  of  30  ohms? 

PROBLEM  15. — If  the  R  of  700  yards  of  copper  wire 
fs  .91  ohms,  what  will  be  the  R  of  1320  yards? 

PROBLEM  16. — The  R  of  a  certain  copper  wire  is  4.55 
ohms.  The  R  of  a  mile  of  this  same  wire  is  1.3  ohms. 
What  is  the  length  of  the  piece  ? 

PROBLEM  17. — If  the  R  of  130  yards  of  copper  wire 
re  of  an  inch  in  diameter  is  i  ohm,  what  is  the  resistance 
of  the  same  length  of  copper  wire  sV  of  an  inch  in  diam- 
eter ? 

PROBLEM  18. — What  is  the  R  of  a  mile  of  copper 
wire  which  has  a  diameter  of  65  mils,  if  the  R  of  a  cop- 
per wire  80  mils  in  diameter  is  8.29  ohms  ?  (A  mil  is  unnr 
of  an  inch). 

PROBLEM  19. — What  length  of  copper  wire  4  mm  in 
diameter  would  be  equivalent  in  resistance  to  12  yards  of 
copper  wire  i  mm  in  diameter? 

PROBLEM  20. — Find  the  joint  R  of  two  wires  offering 
respectively  5  and  7  ohms  resistance. 

PROBLEM  21. — The  joint  resistance  of  two  wires  is 
3  ohms  and  one  of  them  has  a  resistance  of  9  ohms.  What 
is  the  resistance  of  the  other  ? 

PROBLEM  22. — What  must  be  the  resistance  of  the 
shunt  used  with  a  galvanometer  whose  resistance  is  4500 
ohms  so  that  the  resistance  of  the  shunted  galvanometer 
shall  be  450  ohms? 

PROBLEM  23. — Find  the  joint  resistance  of  three  wires 
offering  respectively  5,  n  and  15  ohms. 

PROBLEM  24. — Three  wires  in  a  divided  circuit  have 
resistance  of  6,  7  and  15  ohms  respectively.  How  would 
a  current  of  i  ampere  divide  in  this  circuit  ? 

4 


50  LABORATORY  MANUAL 

PROBLEM  25. — Three  wires  in  divided  circuit  have  a 
joint  resistance  of  6  ohms.  What  resistance  must  be  used 
as  a  shunt  to  reduce  the  joint  R  to  3  ohms? 

PROBLEM  26. — A  galvanometer  whose  resistance  is 
5000  ohms  is  shunted  by  a  wire  having  a  resistance  of  506 
ohms.  If  a  current  of  30  milliamperes  is  sent  through 
the  circuit  what  will  be  the  strength  of  current  through 
the  galvanometer? 

PROBLEM  27. — If  a  current  of  20  ma.  is  passed  through 
the  body,  the  anode  a  circular  disk  of  metal  3  centimeters 
in  diameter  applied  to  the  neck,  the  cathode  10  centi- 
meters square  placed  on  the  abdomen,  what  would  be  the 
density  of  current  per  centimeter  of  surface  at  the  anode  ? 
What  amount  of  electric  energy  (Watts  i.  e.,  C.  X  E.  M.  F.) 
would  be  expended  at  the  anode  in  10  minutes  of  time, 
provided  the  R  at  that  point  is  one-fourth  of  the  entire 
resistance  ? 

PROBLEM  28. — If  the  R,  including  a  portion  of  the 
body,  is  3500  ohms  and  the  skin  contact  with  the  elec- 
trodes furnishes  3000  ohms  of  this  resistance,  how  much 
electric  energy  would  be  expended  at  the  skin  contact  in 
a  treatment  lasting  15  minutes  when  the  voltage  is  50  ? 
What  would  be  the  result?  How  is  that  result  to  be 
avoided? 

PROBLEM  29. — WThen  two  electrodes  each  3  centi- 
meters square  are  used  to  conduct  a  current  of  12.5  ma.  at 
a  voltage  of  70  through  the  spine,  one  electrode  being 
placed  on  the  back  of  the  neck  and  the  other  over  the 
sacrum,  how  much  electric  energy  reaches  the  deep  tissues 
of  the  body  if  the  skin  contacts  furnish  two-thirds  of  the 
entire  resistance  ?  How  could  the  amount  of  energy 
expended  on  the  deeper  portions  be  increased  without 
changing  the  voltage  ? 


PHORESIS,   ANAPHORESIS,   CATAPHORESIS. 


It  has  long  been  known  that  the  direct  electric  cur- 
rent has  a  marked  mechanical  effect  in  carrying  certain 
liquids  and  solutions  through  porous  partitions  or  mem- 
branes so  as  to  either  accelerate  or  retard  the  ordinary 
processes  of  osmosis.  This  effect,  probably  very  closely 
related  to  that  of  electrolysis,  is  generally  such  as  to 
convey  the  substances  in  solution  in  the  liquid  through 
the  dialyzing  partition,  or  membrane  in  the  direction  of  the 
current,  thus  causing  a  decreased  anodal  and  an  increased 
cathodal  pressure,  although  in  some  instances  the  reverse  of 
this  is  true.  These  phenomena,  which  are  most  manifest 
in  badly  conducting  liquids,  are  generally 
included  under  the  term  electric  osmose 
but  when  applied  to  living  animal  tissues 
for  therapeutic  purposes  are  called  cata- 
phoresis  or  anaphoresis  according  to 
the  direction  in  which  the  substance  is 
conveyed. 

The  numerous  experiments  of  De  la 
Rive  established  the  following  generaliza- 
tions regarding  electric  endosmose: 

''The  force  with  which  a  galvanic 
current  transports  a  liquid  through  a  por- 
ous partition  from  the  positive  to  the 
negative  wall  is  measured  by  a  pressure 
which  is  directly  proportional  to  the  intensity  of  the 
current,  to  the  electric  resistance  of  the  liquid,  to  the 
thickness  of  the  porous  partition,  and  inversely  propor- 
tional to  the  surface  of  that  partition." 


Pig.  29  Phoresiis 
electrode. 


•52 


LABORATORY  MANUAL 


EXPERIMENT  60.  —The  passage  of  substances  into  or 
out  of  the  tissues  of  the  body  may  be  hastened  by  electric 
osmosis,  that  is  by  the  anaphoric  or  cataphoric  action  of 
the  current.  Thoroughly  wash  your  hands  with  soap  and 
water,  then  place  on  the  back  of  each 
wrist  a  square  cotton-covered  electrode 
which  has  been  saturated  in  a  solution  of 
methylene  blue.  Now  pass  the  current 
from  your  8-cell  battery  through  the  body 
from  wrist  to  wrist.  Measure  carefully 
the  current  and  allow  it  to  flow  till  the 
equivalent  of  5  ma.  has  passed  for  10 
minutes.  Discontinue  the  current  and 
again  wash  the  wrists  and  examine 
whether  there  is  any  difference  in  the 
discoloration  of  the  skin  which  was 
under  tne  anode  and  cathode. 

EXPERIMENT  61. — Repeat  the  last 
experiment  employing  a  cathode  moistened  with  a  solution 
of  common  salt  and  a  metallic  or  better  a  carbon  anode 
separated  from  the  skin  by  two  small  squares  of  blotting 
paper  soaked  in  a  4  per  cent,  solution  of  cocaine  hydro- 
chloride.  The  current  should  be  measured  carefully  and 
permitted  to  pass  for  at  least  ten  minutes.  When  it 
is  discontinued  the  part  under  the  electrode  should  be 
examined  to  see  whether  any  local  anaesthesia  has  been 
produced.  This  can  be  tested  by  pricking  the  surface 
with  a  needle. 

Electric  osmosis,  either  as  anaphoresis  or  cataphor- 
esis,  is  employed  in  electro-therapeutics  for 

i  st.  Conveying  medicines  in  solution  into  the  tissues 
through  the  skin  or  mucous  membrane  surfaces.  This 
can  be  made  local  or  general  medication  according  as  a 


Fig.  30  Section  of 
Phoresi*  Electrode. 


OF    ELECTROTHERAPEUTICS.  53 

limited  area  or  the  entire  skin  surface  is  subjected  to  the 
action; 

2nd.  Removing  injurious  substances  from  the  tissues, 
abnormal  accumulations  of  fluids  in  joints,  dropsical 
effusions,  etc. 

Cataphoresis  is  at  present  much  used  by  the  dentist 
to  obtund  sensitive  dentine.  The  anodal  effect  of  the 
current  is  of  itself  sedative  but  its  anaesthetic  action  is 
greatly  increased  when  a  substance,  which  is  soothing  to 
sensory  nerves  and  is  capable  of  being  conveyed  into  the 
tissues  by  means  of  cataphoric  action,  is  used  in  solution 
on  the  anode. 

PHYSIOLOGICAL  ACTION  OF  DIRECT  CURRENTS. 


There  are  certain  reactions  which  direct  or  galvanic 
currents  bring  about  when  applied  to  living  animal  tissues 
which  cannot  be  regarded  as  physical  or  mechanical  effects 
of  the  current,  since  they  are  dependent  upon  the  pecu- 
liar properties  of  living  animal  tissues  and  the  nature  of 
their  response  as  such  to  this  form  of  stimulant  or  excit- 
ant. These  it  seems  proper  to  designate  as  physiological 
effects,  and  as  they  have  long  served  as  a  rational  basis 
for  therapeutic  applications  with  this  form  of  current  a 
special  mention  of  them  is  required.  The  physiological 
effects  that  are  best  known  to  us  from  experiments  in  the 
physiological  laboratory  and  from  electro-therapeutic 
observations  may  be  classified  as: 

Reactions  of  muscular  tissue; 

Reactions  of  nerve  tissue; 

Reactions  of  protoplasm. 

Both  the  striped  and  unstriped  varieties  of  muscle 
can  be  caused  to  contract  by  the  application  to  them  of 


54  LABORATORY  MANUAL 

either  pole  of  a  direct  current,  the  other  pole  being  placed 
upon  some  distant  point  of  the  body  to  complete  the 
circuit.  The  strength  of  the  response  in  normal  muscle 
will  depend  upon  the  strength  and  electro-motive  force  of 
current  used.  This  form  of  current  causes  a  contraction 
only  at  the  moment  when  it  is  closed  or  opened;  at  the 
"make"  and  "break"  of  the  currents  as  they  are  called. 
The  reactions  in  unstriped  muscle  resemble,  in  general, 
those  of  the  striped  variety  except  that  unstriped  muscle 
responds  more  slowly  to  the  stimulation. 

The  results  following  the  application  of  the  direct 
current  to  nerve  tissue  differs  according  to  the  nature  of 
the  tissue  influenced  /'.  e.,  whether  it  is  peripheral  nerve, 
sensory,  motor,  secretory  or  nerve  cells  in  brain,  cord,  or 
ganglia.  Thus,  applications  along  the  course  of  a  motor 
nerve  will  cause  contractions  in  the  muscle  supplied  by 
that  nerve  similar  to  those  obtained  by  the  direct  applica- 
tion to  the  muscle  itself. 

Sensory  nerves  respond  to  direct  current  applications 
by  increase  or  decrease  of  excitability,  according  as  the 
application  is  made  with  the  anode  or  cathode.  The 
result  of  anodal  application  is  to  decrease  the  excitability 
and  the  effect  is  called  anelectrotonus.  The  result  of 
the  cathodal  application,  on  the  other  hand,  is  to  increase 
the  excitability  and  this  effect  is  called  catelectrotonus. 

EXPERIMENT  62. — Join  two  experimental  batteries  in 
series,  put  in  circuit  the  galvanometer,  B  terminals,  a 
circuit  breaker,  pole  changer  and  a  high-resistance  rheo- 
stat. Use  a  large  dispersing  cotton-covered  electrode  and 
a  small  active  electrode  which  should  be  applied  over  the 
median  nerve  above  the  elbow  joint.  By  means  of  the 
pole-changer  the  small  electrode  can  be  quickly  changed 
from  anode  to  cathode  and  the  current  strength  can  be 


OF    ELECTROTHERAPEUTICS.  55 

readily    changed   by  means   of    the    rheostat.       Carefully 
determine  the  strength  of  current  that  will  produce: — 

1.  Cathode  closing  contraction    (C.  C.  C. ). 

2.  Anode  closing  contraction        (A.  C.  C. ). 

3.  Anode  opening  contraction      (A.  O.  C.). 

4.  Cathode  opening  contraction  (C.  O.  C. ). 

This  experiment  may  be  done  by  four  students  work- 
ing together.  Make  a  sketch  of  the  entire  circuit. 

EXPERIMENT  63. — Apply  two  cotton-covered  elec- 
trodes about  1.5  inches  square  to  corresponding  parts  of 
the  flexor  surface  of  each  forearm.  Place  a  rheostat,  gal- 
vanometer and  a  i6-cell  battery  in  circuit  and  allow  a 
current  of  10  ma.  to  flow  for  at  least  5  minutes.  After 
the  electrodes  have  been  removed  apply  the  points  of  a 
pair  of  compasses  to  the  two  surfaces  and  in  each  case 
determine  the  distance  between  the  points  in  millimeters 
at  which  they  can  be  distinguished  by  sensation  alone. 
Can  you  detect  any  difference  in  the  sensibility  of  the 
two  surfaces?  Also  note  any  difference  in  the  external 
appearance  of  the  two  surfaces  which  were  under  the 
influence  of  the  current. 


CATALYSIS. 


The  term  catalysis  was  first  employed  by  'Remak  to 
include  the  various  processes,  partly  demonstrable  and 
partly  theoretical,  which  attended  the  application  of  a 
direct  current  to  diseased  tissues  and  which  often  resulted 
in  a  restoration  of  normal  function.  These  processes  are 
both  physical  and  physiological,  some  of  them  being  of  a 
very  complex  nature. 

It  is  believed  that  neither  the  electrolytic,  cataphoric, 


56  LABORATORY  MANUAL 

anaphoric,  contractile,  nor  electrotonic  actions  of  the 
direct  current  which  have  already  been  described  are  suffi- 
cient to  account  for  the  permanent  benefit  which  the 
employment  of  such  currents  in  therapeutics  affords.  It 
is  assumed  therefore  that  there  are  a  variety  of  effects  not 
yet  experimentally  demonstrable  but  still  theoretically 
quite  probable,  that  follow  from  the  passage  of  the  cur- 
rent in  addition  to  these  that  can  be  readily  observed,  and 
it  is  both  these  known  and  assumed  actions  that  the  word 
catalysis  is  intended  to  cover.  The  result  you  obtained  in 
EXP.  59  will  serve,  in  a  measure,  to  illustrate  this  inter- 
polar  action  of  the  direct  current  when  passed  through 
the  living  organism. 


THE  GALVANO-CAUTERY. 

The  energy  of  an  electric  current  may  manifest  itself 
in  a  variety  of  ways,  such  as  magnetic,  mechanical, 
chemical  and  radiant  energy,  the  latter  including  various 
phenomena  among  which  the  most  common  are  heat  and 
light.  In  every  case  where  a  current  is  controlled  by  the 
introduction  of  resistance  into  the  circuit,  without  a 
counter  electro-motive  force  such  as  is  furnished  by  an 
electric  motor  or  an  electrolytic  cell,  the  energy  is  used 
up  in  the  form  of  heat.  In  the  vast  majority  of  electrical 
operations  the  heating  effects  of  the  currents  are  wasteful 
and  are,  so  far  as  possible,  avoided  or  reduced  to  a  mini- 
mum. The  electric  cautery  is  one  of  the  appliances  in 
which  this  property  of  the  current  can  be  utilized.  The 
amount  of  heat  developed  in  a  conductor  is  proportional— 

ist,  to  the  resistance; 

2nd,  to  the  square  of  the  strength  of  current;  and 

3d,  to  the  time. 


OF    ELECTROTHERAPEUTICS.  57 

The  temperature  to  which  a  body  of  a  given  resist- 
ance will  be  raised  by  a  given  current  depends  upon  the 
nature  of  the  resisting  substance,  /'.  e.  upon  its  specific 
heat,  and  also  upon  the  form  of  the  conductor.  The 
temperature  will  continue  to  rise  till  the  rate  at  which  it  is- 
lost  by  conduction,  convection  and  radiation  is  equal  to 
the  rate  of  generation  by  the  current. 

From  these  general  considerations  it  becomes  evident 
that  all  parts  of  the  circuit  in  cautery  work  should  have 
the  least  possible  resistance  except  the  part  which  is  to  be 
heated.  For  this  reason  cautery  batteries  are  made  of 
large  plates  placed  very  close  together  and  all  the  neces- 
sary conducting  wires  are  relatively  large  and  of  low 
resistance  (T.  426 — 429). 

EXPERIMENT  64.  —To  show  the  necessity  of  a  strong 
current  in  working  with  the  cautery,  connect  the  poles  of 
your  battery,  arranged  two  in  series  and  four  in  multiple 
arc,  by  ten  inches  of  No.  36  copper  wire.  Observe  to 
what  extent  the  wire  is  heated  and  then  slowly  shorten  it 
and  notice  whether  the  temperature  rises.  Repeat,  this 
time  using  german  silver  wire  of  the  same  length  and 
diameter. 

EXPERIMENT  65.  —  Show  the  necessity  of  having  a 
low  internal  resistance  by  using  first  one  cell  of  the  experi- 
mental battery  and  then  one  of  the  large  bichromate  cells 
on  the  side  table,  in.  each  case  passing  the  current  through 
the  german  silver  wire  used  in  the  last  experiment.  Is  the 
effective  E.  M.  F.  in  the  two  cells  the  same  after  the  cur- 
rent has  been  flowing  a  few  minutes  ?  Give  your  reasons. 

EXPERIMENT  66. — Twist  together  three  pieces  of 
iron  or  german  silver  wire  six  inches  in  length  and  pass 
the  current  of  your  battery  joined  in  multiple  arc  through 
it.  Notice  the  rise  in  temperature.  Now  replace  the 


58  LABORATORY  MANUAL 

twisted  strand  by  a  single  wire  two  inches  in  length,  and 
see  whether  the  temperature  is  higher  than  before.  Is  the 
strength  of  current  the  same  in  the  the  two  cases?  How 
do  you  explain  the  difference  in  the  results?  (T.  429). 


Fig.  31.    Primary  Battery  for  Cantery  Work. 

• 

The  heat  generated  in  the  two  cases  should  be  exactly  the 
same  but  the  mass  of  metal  and  surface  exposed  in  the 
two  cases  are  very  unequal.  It  should  be  apparent  that 
wires  having  a  high  specific  resistance  and  which  do  not 
easily  corrode  are  best  adapted  for  use  in  the  cautery. 
Platinum  meets  these  requirements  and  has  the  additional 


OF    ELECTROTHERAPEUTICS.  59 

advantage  of  not  being  easily  fused;  even  it,  however,  can 
be  melted  by  the  electric  current. 

EXPERIMENT  67. — Make  a  small  cautery  electrode 
like  the  model  shown  you.  Connect  it  to  one  of  the 
large  bichromate  cells.  What  causes  the  rapid  falling  in 
temperature  after  the  current  has  been  flowing  a  few  min- 
utes ?  Notice  the  effect  of  raising  and  lowering  the  plates 
in  the  fluid.  Examine  the  two  forms  of  cautery  batteries 
and  the  methods  of  controlling  the  current  in  each.  It  is 
evident  that  the  plates  should  be  left  in  the  fluid  only  so 
long  as  the  cautery  is  in  immediate  use.  Could  you  heat 
a  cautery  with  six  Daniell  cells? 

EXPERIMENT  68. — Use  one  of  the  cautery  batteries 
to  heat  the  cautery  electrode  and  when  it  is  glowing, 
immerse  part  of  it  in  water  and  notice  the  effect  on  the 
remaining  part  of  the  fine  wire.  What  is  your  explana- 
tion? A  similar  effect  attends  the  use  of  the  cautery  in 
practice  and  unless  a  ready  means  of  regulating  the  cur- 
rent is  at  hand,  it  may  be  melted  (T.  404). 

SOURCES  OF  CURRENT  FOR  THE  ELECTRIC  CAUTERY. 

The  strength  of  current  required  for  heating  electric 
cauteries  varies  from  i  to  25  amperes.  This  current  is 
far  in  excess  of  that  used  in  therapeutics  when  the  current 
traverses  the  body,  and  for  this  reason  special  forms  of 
generators  and  controllers  are  required  for  doing  cautery 
work.  A  suitable  current  may  be  obtained  from: — 

1.  Primary  batteries. 

2.  Secondary  or  storage  batteries. 

3.  The  dynamo. 

Primary  Batteries. — Since  the  external  resistance 
in  a  cautery  circuit  is  very  small  (seldom  exceeding. i 
ohm)  it  is  necessary  that  a  cautery  battery  should  be 


6o 


LABORATORY  MANUAL 


specially  constructed  so  that  its  internal  resistance  shall 
be  reduced  to  a  minimum.  The  E.  M.  F.  may  vary  from 
2  to  6  volts.  In  order  to  deminish  the  internal  resistance 
of  a  battery,  the  plates  should  be  large  and  near  together 
and  every  precaution  should  be  taken  to  prevent  polariza- 
tion. If  cells  of  large  size  are  inconvenient  and  make 
the  battery  too  cumbersome,  smaller  cells  may  be  em- 


Fig.  32. 

ployed  provided  they  are  joined  in  multiple  arc.  By 
using  a  large  bichromate  cell  with  large  plates  of  carbon 
and  zinc  the  resistance  may  be  brought  down  to  .15  ohms. 
This  cell  acting  through  a  cautery  electrode  of  .  i  ohm 
resistance  would  furnish  8  amperes  of  current. 

E 


C  = 


22 

C  =  -  -  =  8  amperes. 

o.i  +  0.15        0.25 


R  -j-  r 

In  all  forms  of  primary  batteries  which  generate  large 
currents,  polarization  soon  tends  to  lessen  the  output  of 
current.  This  difficulty  may  be  prevented  by  keeping  the 


OF    ELECTROTHERAPEUTICS.  6l 

plates  of  the  battery  constantly  in  motion,  thus  bringing 
fresh  battery  fluid  in  contact  with  the  plates.  By  having 
at  the  outstart  a  current  capacity  far  in  excess  of  the 
amount  required  to  heat  the  cautery,  a  suitable  rheostat 
in  circuit  to  regulate  the  current  to  the  required  amount 
would  be  the  most  convenient  method  of  overcoming  the 
polarization  effects. 

Secondary  or  Storage  Batteries. — A  well  con- 
structed and  newly  charged  storage  battery  furnishes  an 
ideal  source  of  current  for  cautery  purposes.  The  current 
should  be  controlled  by  a  rheostat  such  as  has  already 
been  mentioned.  The  care  of  a  storage  battery  and  the 
uncertainty  of  its  charge  at  any  time  are  drawbacks  which 
prevent  its  general  use  by  physicians. 

.  Dynamo  Circuits.  — The  currents  from  both  direct 
and  alternating  current  dynamos  may  be  controlled  by 
heavy  wire  resistance  for  heating  electric  cauteries.  This 
is  however  a  cumbersome  aud  expensive  method. 

When,  however,  these  currents  are  changed  by  trans- 
formers they  become  the  most  convenient  sources  of  cur- 
rent for  electro-cauteries  and  exploring  lamps,  this  being 
especially  true  of  the  transformed  alternating  current. 

Attention  will  be  given  to  these  methods  of  transfor- 
mation of  dynamo  currents  further  on  in  this  work. 


SOURCES  OF  CURRENT  FOR  ELECTRIC  LIGHT. 


The  electric  light  possesses  marked  advantages  over 
all  other  means  for  illuminating  the  cavities  of  the  body 
In  general,  it  may  be  stated 
that  the  sources  of  current  for 
electric  cauteries  will  also 
serve  to  light  the  exploring 
lamps  used  for  diagnosis  or  illu- 
mination. The  conditions  of  the  circuit  are, 
however,  somewhat  changed  and  these  de- 
mand corresponding  changes  in  the  source 
of  the  current  Thus,  the  resistance  of  the 
filament  of  the  small  lamps  varies  from  6  to 
30  ohms.  The  current  strength  required  to 
raise  these  lamps  to  incandescence  is  from 
3  to  1.6  amperes.  Thus  a  greater  E.  M-.  F. 
is  necessary  than  for  heating  a  cautery  and 
the  internal  resistance  becomes  a  factor  of 
very  aiuch  less  importance.  A  battery  of  10 
bichromate  cells  in  series,  when  r  =  i  ohm, 
would  send  a  current  of  i  ampere  through  a 
lamp  of  10  ohms  resistance. 

2  X  10 


C  = 


20 


-, x — : =  --  =  i  ampere. 

(i     X    10)   -f    10  20 


Fig.  33  Tongue 
depressor  and 
throat  illu- 
minator. 


In  lighting  lamps  to  be  used  in  diagnosis 
it  is  necessary  that  the  current  be  controlled  either  by  a 
rheostat  or  by  some  ready  means  for  varying  the  E.  M.  F. 
acting  through  the  lamp.  The  transformed  alternating 


OF    ELECTROTHERAPEUTICS.  63 

dynamo  current  is  a  most  desirable  and  convenient  source 
to  employ  for  this  purpose. 


THE  STORAGE  OR  SECONDARY  BATTERY. 


As  was  seen  in  EXP.  55,  a  difference  of  potential 
exists  between  two  like  plates  immersed  in  a  liquid,  by 
virtue  of  the  products  of  electro-chemical  decomposition 
set  free  at  their  surfaces.  Such  cells  are  known  as  storage 
cells  or  accumulators.  The  E.  M.  F.  of  the  accumulator 
depends  upon  the  tendency  for  the  liberated  "ions  "to 
recombine  and  its  magnitude  is  strictly  proportional  to 
the  energy  with  which  this  recombination  tends  to  take 
place.  Thus,  in  the  electrolysis  of  water,  the  elements  O 
and  H  by  their  recombination  yield  an  E.  M.  F.  of  1.47 
volts  and  consequently  no  cell  or  other  source  of  current 
can  effect  the  electrolysis  of  water  unless  it  has  an  electro- 
motive force  of,  at  least,  1.47  volts.  It  should  be  borne 
in  mind  that  it  is  not  electricity  but  chemical  energy 
which  is  stored  up  by  the  current  and  thac  the  latter  under 
proper  conditions  is  again  reconverted  or  transformed 
into  the  energy  of  an  electric  current.  In  the  progress  of 
development  of  the  storage  cell  two  main  problems  were 
prerented,  viz:  — 

1.  How  to   retain   a   large   amount   of  the  liberated 
"ions"  upon  the  two  electrodes, 

2.  How   to    prevent   the  dissipation   of    the   energy 
while  the  cell  is  on  open  circuit. 

Considerable  advancement  has  been  made  in  recent 
years  but  the  second  problem  has  proved  to  be  far  the 
more  difficult  to  solve. 


64  LABORATORY  MANUAL 

Great  care  must  be  exercised  in  the  handling  of  a 
storage  battery  as  an  accidental  "  short  circuit "  is  very 
destructive  to  the  plates.  In  charging  the  cell  the  direc- 
tions of  the  manufacturer  should  be  strictly^  observed  and 
where  practicable  it  is  best  to  entrust  this  task  to  the 
manufacturer  or  to  some  local  electrician. 

A  recent  form  of  storage  battery  is  one  consisting 
practically  of  two  lead  plates,  the  positive  of  which  is 
intimately  covered  with  red  lead  (minium,  P£3O4)  and  the 
negative  with  litharge  (P^O).  The  electrolyte  is  sul- 
phuric acid,  one  part  by  weight  to  four  of  water.  As 
soon  as  the  plates  are  immersed  in  the  fluid  the  following 
reaction  takes  place.  The  lead  oxides  are  converted  into 
lead  sulphate. 

P£3O4  +  2H2SO4  =  P£02  +  2P£SO4  +  2H2O. 

The  changing  current  liberates  hydrogen  and  oxygen. 
The  latter  goes  to  the  positive  plate  and  changes  the  lead 
sulphate  to  lead  peroxide  and  sulphuric  acid. 

2P£SO4  +  2H2O  -f  O2  =  2P£O2  +  2H2SO4. 

Hydrogen  goes  to  the  negative  plate  and  changes  the 
lead  monoxide  to  spongy  lead  with  the  formation  of  water. 

P£O  +  H2  =  P£  +  H2O. 

It  also  acts  upon  the  lead  sulphate,  changing  it  to 
spongy  lead  and  sulphuric  acid. 

2P^SO4  +  2H2  =  2P£  +  2H2SO4. 

The  chemical  reaction  of  the  discharge  is  the  forma- 
tion of  lead  sulphate  upon  both  plates. 

EXPERIMENT  69. — Construct  a  storage  battery,  using 
lead  plates  with  a  paste  made  of  lead  oxide  and  sulphuric 
acid  (1:4),  held  in  place  by  a  layer  of  absorbent  cotton. 


OF  ELECTROTHERAPEUTICS.  65 

Roll  the  plates  tightly  together,  being  careful  to  have 
them  completely  covered  with  cotton,  and  then  immerse 
in  the  sulphuric  acid  solution.  To  get  good  results  it 
is  advisable  to  first  charge  and  then  discharge  the  bat- 
tery. First  pass  the  charging  current  in  one  direction, 
then  reverse  the  current  and  finally  pass  it  again  in  the 
first  direction.  Connect  the  plate  covered  with  lead  to 
the  positive  pole  while  charging.  When  your  accumulator 
is  finally  charged  have  its  E.  M.  F.  measured  and  then 
proceed  to  determine  its  internal'  resistance  by  Ohm's 
law.  From  these  results  compute  the  current  which  the 
cell  would  furnish  when  working  on  short  circuit. 

NOTE.  —Your  experimental  battery  must  be  in  good  condition  for 
charging  and  it  is  well  to  join  it  2  in  multiple  arc  and  4  in  series.  The 
time  required  for  each  charge  and  discharge  should  be  at  least  10  min- 
utes. The  galvanometer  may  be  used  to  assure  you  that  you  have  a 
charging  current  and  to  detect  any  variations  in  the  same. 


THE  ROTARY  TRANSFORMER. 


The  rotary  transformer  shown  in  the  accompanying 
figure  is  a  device  for  changing  the  ordinary  direct  dynamo 
current  of  high  voltage  to  a  direct  current  of  low  voltage 
such  as  is  suitable  for  heating  cautery  wires  and  lighting 
exploring  lamps.  The  machine  is  virtually  an  electric 
motor  and  dynamo  combined,  the  current  supplied  to  the 
motor  being  of  a  higher  E.  M.  F.  than  that  furnished  by 
the  dynamo.  Except  for  a  slight  loss  in  transformation 
the  energy  (C.  V.  =  current  X  potential  difference)  sup- 
plied to  the  machine  and  that  yielded  by  it  should  be 
equal.  The  old  method  of  controlling  dynamo  currents 
for  cautery  work  by  introducing  heavy  wire  resistance  in 

5 


66 


LABORATORY  MANUAL 


circuit  is  both  very  cumbersome  and  expensive  since  less 
than  10  per  cent,  of  the  energy  is  usefully  employed. 

A  similar  waste  of  en- 
ergy can  be  obviated  by 
charging  storage  batter- 
ies with  the  transformed 
current  instead  of  em- 
ploying the  ordinary  dy- 
namo current  controlled 
by  resistance. 

A  suitable  rheostat 
must  be  employed  in 
the  cautery  or  light  cir- 
cuit for  the  purpose  of 
controlling  the  current 
more  accurately. 
Fig.  34.  Rotary  Transformer.  The  rotary  transform- 

er is  not  only  a  conven 

ient  and  economical  means  for  securing  a  direct  current 
for  therapeutic  purposes  but  it  is  also  a  safe  means.  When 
taking  a  supply  of  current  for  therapeutic  purposes  from 
dynamo  mains  carrying  a  current  of  high  voltage  all  danger 
of  subjecting  a  patient  to  an  excess  of  current  or  voltage 
is  entirely  removed  by  this  device. 


MAGNETISM. 


A  close  relationship  exists  between  current  electricity 
and  magnetic  phenomena.  Induced  current  electricity, 
which  plays  a  very  important  part  in  therapeutics,  is  the 
result  of  magnetic  action.  There  is  also  good  reason  to 
believe,  from  the  results  of  recent  investigations,  that 
magnetism  itself  has  some  direct  therapeutic  value.  At 
least  we  have  discovered  from  experiments  conducted  for 
a  number  of  months  in  this  laboratory  that  the  growth  of 
growing  animals  is  accelerated  when  subjected  for  some 
time  to  the  influence  of  alternating  magnetic  fields.  These 
considerations  render  it  advisable  for  us  to  review  by 
experiment  the  fundamental  phenomena  relating  to  the 
relationship  between  electricity  and  magnetism. 

In  performing  the  following  experiments  certain  facts 
should  be  kept  in  mind: 

1.  Rough    and    careless    handling    of    a    permanent 
magnet  is  very  detrimental  to  its  strength  and  may  destroy 
its  usefulness; 

2.  The   swinging   needle   of    the   galvanometer   may 
have   its   magnetic   properties    changed    or    destroyed    by 
bringing  strong  magnets  too  near  it  and   thus   the   instru- 
ment may  be  rendered  quite  useless. 

EXPERIMENT  70. — Upon  a  smooth  white  surface  place 
a  small  quantity  of  iron  filings.  Bring  a  soft  iron  bar  in 
contact  with  them  and  notice  whether  they  attach  them- 
selves to  its  surface.  Also  bring  a  steel  bar  in  contact 
with  them  and  observe  whether  they  behave  as  before. 

EXPERIMENT  71. — Hold  the  end  of  the  soft  iron  bar 
among  the  filings  and  while  it  is  there  bring  a  permanent 


68  LABORATORY  MANUAL 

magnet  in  contact  with  the  other  end;  observe  whether  or 
not  any  filings  cling  to  the  iron  bar.  Remove  the  perma- 
nent magnet  and  observe  what  takes  place.  Proceed  in 
the  same  manner  with  the  hard  steel  bar.  Does  it  support 
as  many  filings  as  does  the  iron  bar?  Do  they  all  drop  off 
on  removing  the  permanent  magnet?  Try  to  magnetize 
the  iron  permanently  by  rubbing  it  with  the  permanent 
magnet,  also  try  the  same  with  the  steel  bar.  Note  the 
results.  What  part  of  the  bar  will  support  the  greatest 
weight?  (T.  86). 

EXPERIMENT  72. — Float  a  small  magnetized  steel  bar 
(a  piece  of  watch  spring  answers  very  well)  by  means  of 
a  flat  cork  in  a  flat  porcelain  dish  nearly  filled  with  water. 
Notice  that  it  comes  to  rest  with  its  ends  pointing  north 
and  south.  (T.  87).  When  the  bar  is  at  rest  bring  first 
near  its  north  end  and  then  near  its  south  end  a  bar  of 
soft  iron.  Notice  in  each  case  the  effect  on  the  magnet- 
ized bar.  Remove  the  end  of  the  soft  bar  and  see 

« 

whether  the  effect  differs. 

EXPERIMENT  73. — With  the  steel  bar,  as  in  the  pre- 
ceding experiment,  bring  near  its  north  seeking  end  first 
one  pole  and  then  the  other  of  a  small  bar  magnet. 
Notice  that  the  pole  that  attracts  the  north  seeking  end  of 
the  floating  bar  repels  the  south  seeking  end  and  vice  versa. 
Remove  the  bar  from  the  cork  and  bring  the  end  that 
pointed  north  near  either  end  of  the  galvanometer  needle. 
Notice  that  it  attracts  the  south  seeking  end  but  repels  the 
north  seeking  end,  behaving  as  did  the  bar  in  the  first  part 
of  the  experiment. 

EXPERIMENT  74. — Magnetize  a  piece  of  watch  spring 
and  after  determining  its  polarity,  break  it  in  two  and  see 
what  relation  the  poles  of  one  piece  bear  to  those  of  the 
other  (T.  88,  89,  90,  91,  96,  97.).  Is  it  possible  to  mag- 


OF    ELECTROTHERAPEUTICS.  69 

netize  a  watch  spring  in  such  a  manner  that  it  shall  have 
three  or  more  poles?     If  so  explain  the  process. 

EXPERIMENT  75. — Place  a  smooth  piece  of  paper 
over  a  bar  magnet  which  is  sunk  beneath  the  surface  of  a 
small  board.  Sift  iron  filings  through  a  piece  of  cloth 
evenly  over  the  surface  of  paper  and  tap  it  lightly.  The 
filings  will  arrange  themselves  in  well  defined  curved  lines 
around  the  magnet.  Make  a  sketch  of  the  magnetic  field 
thus  shown.  Also  in  like  manner  prepare  and  draw  the 
magnetic  fields  between  two  similar  and  two  opposite 
magnetic  poles.  What  direction  is  attributed  to  magnetic 
lines  of  force  (i)  within  the  magnet  and  (2)  in  the  mag- 
netic field?  Can  the  number  of  magnetic  lines  of  force 
in  a  permanent  magnet  be  varied  by  causing  an  armature 
to  approach  or  recede  from  it?  (T.  375-377). 

MAGNETIC  EFFECTS  OF  THE  ELECTRIC  CURRENT. 

The  following  are  a  few  of  the  most  important  laws 
relating  to  the  magnetic  effects  of  electric  currents: 

1.  A  piece  of  soft  iron  surrounded  by  a  coil  or  helix 
of    insulated    wire    becomes   a    magnet    and    retains    that 
property  while  an  electric  current  is   flowing  through  the 
helix. 

2.  The  strength  of  an  electro-magnet  is  proportional 
to  the  strength  of  current  and  to  the  number  of  turns  of 
wire  in  the  helix — in  other  words,  is  proportional  to  the 
number  of  ampere  turns.      This   law   is   only  true  so  long 
as  the  iron  core,  is  still  unsaturated. 

3.  Upon  interrupting  the   current   in   the   helix   the 
magnetism  induced  in  the  iron  at  once  disappears.      Nearly 
all  specimens  of  iron  retain  a   trace   of    magnetism   for   a 
time,  the  amount  retained  and  the  time  depending  on  the 
quality  of  the  iron.      (T.  367,  368). 


7°  LABORATORY  MANUAL 

4.  If  the  iron  core  or  bar  be  removed  from  the  helix 
the  latter  will  act,  while  the  current  is  flowing,  like  an 
electro-magnet  but  to  a  much  smaller  degree  than  when 
the  core  is  present.  If  the  core  be  made  up  of  a  large 
number  of  small  bars  it  will  both  receive  and  give  up 
its  magnetic  properties  more  readily.  (T.  381,  382,  383, 

384). 

EXPERIMENT  76. — Having  a  soft  iron  bar,  wind 
around  it  from  one  end  to  the  other  an  insulated  copper 
wire.  Having  one  end  of  the  bar  held  in  position  near 
some  iron  filings  and  a  small  bichromate  cell  connected  to 
the  wires,  observe  what  takes  place  upon  making  and 
breaking  the  circuit.  Again  bring  one  end  of  the  electro- 
magnet near  the  galvanometer  needle  and  on  completing 
the  circuit  notice  that  the  north  seeking  end  is  either 
attracted  or  repelled.  (Avoid  bringing  it  too  near).  What 
is  the  polarity  of  the  end  presented?  Present  the  oppo- 
site end  of  the  electro-magnet  and  see  whether  the  result 
differs.  Rewind  the  bar  in  the  opposite  direction  and 
observe  whether  the  polarity  has  been  changed.  You  should 
be  able  to  deduce  the  law  which  shows  the  relation  between 
the  direction  of  the  current  around  the  helix  to  the  magneti- 
zation produced. 

EXPERIMENT  77. — With  the  iron  bar  used  before  wind 
the  wire  midway  between  the  ends,  using  the  same  number 
of  turns  and  covering  not  more  than  one- third  of  the  bar. 
Compare  the  strength  with  that  of  the  covered  bar.  This 
can  be  done  by  allowing  it  to  pick  up  small  pieces  of  iron 
or  preferably  by  observing  the  deflection  produced  on  the 
galvanometer  needle  at  a  given  distance.  Place  the  coil 
at  one  extremity  of  the  bar  and  compare  the  result  with 
the  preceding.  In  all  cases  the  wire  should  be  evenly  and 
closely  wound  around  the  bar,  and  in  each  case  the  plates 


OF    ELECTROTHERAPEUTICS.  71 

of  the  battery  must  be  removed  from  the  liquid  as  soon  as 
the  observation  is  made.      Why  ? 

EXPERIMENT  78. — With  the  coil  at  one  extremity  of 
the  bar  remove  the  wire,  one  turn  at  a  time,  and  observe 
each  time  the  change  in  the  strength  of  the  magnet. 
What  are  the  constant  and  what  the  varying  factors  in 
this  experiment? 

EXPERIMENT  79. — Having  the  coil  at  one  end  of  the 
bar  either  replace  the  small  battery  by  a  large  one  or 
introduce  a  resistance  into  the  circuit  without  changing 
the  number  of  turns  on  the  bar.  Observe  the  variation 
in  the  strength  of  the  magnet.  Would  you  expect  it  to 
vary  the  same  way  in  either  case? 

EXPERIMENT  80. — Now  with  the  soft  iron  bar  and  the 
helix  arranged  as  in  the  preceding  experiment,  bring  one 
extremity  near  some  small  iron  nails.  Notice  that  they 
cling  to  it  only  as  long  as  the  current  is  flowing.  Replace 
the  bar  with  one  of  harder  iron  and  repeat,  noticing 
results.  Finally  use  a  steel  bar  in  place  of  the  iron  and 
compare  results  with  those  obtained  with  the  other  bars 
(T.  381  to  385). 

EXPERIMENT  8 1. — Float  the  bar  of  magnetized  steel 
upon  a  cork,  pass  over  and  parallel  to  it  a  copper  wire 
connected  to  your  voltaic  cell  so  that  you  can  cause  a 
current  to  pass  through  it.  Is  there  any  action  mani- 
fested between  the  "live  "  wire  and  the  magnet  when  they 
are  not  in  contact?  If  so,  to  what  is  it  due  and  what  will 
you  call  the  force?  Now  pass  the  current  beneath  and 
parallel  to  the  needle  and  on  closing  the  circuit  notice  in 
what  manner  the  deflection  varies  from  that  in  the  first 
part  of  the  experiment.  What  would  be  the  effect  of 
changing  the  direction  of  the  current  in  the  wire? 


72  LABORATORY  MANUAL 

What  two  ways  of  reversing  a  deflection  have  you  discov- 
ered ?  (T.  195,  196,  197). 

EXPERIMENT  82. — Modify  the  last  experiment  by 
floating  your  galvanometer  so  that  its  coil  stands  at  right 
angles  to  its  needle,  which  will  be  the  case  when  the 
needle  points  to  90°  on  the  scale.  Pass  the  wire  over  and 
parallel  to  the  needle.  On  completing  the  circuit  notice 
that  the  needle  behaves  as  did  the  bar  in  the  last  experi- 
ment. 

EXPERIMENT  83. — Having  the  galvanometer  as  in  the 
last  experiment,  wind  a  wire  once  around  so  that  the 
needle  shall  lie  within  the  coil  and  observe  whether  the 
deflection  is  increased.  Increase  the  turns  of  the  wire 
and  observe  whether  the  deflection  is  increased  with  each 
additional  turn  (T.  200).  Use  insulated  wire  in  this 
experiment. 

EXPERIMENT  84. — With  your  insulated  wire  form  an 
oblong  coil  2x^  inches  made  of  six  turns.  Connect  its 
terminals  with  the  wires  from  your  voltaic  cell.  Hold  the 
coil  just  above  and  parallel  to  the  needle  of  the  galvano- 
meter. When  the  current  is  sent  through  the  coil  com- 
pare the  deflection  produced  with  that  in  the  previous 
experiment  using  the  same  number  of  turns  of  wire. 
How  can  you  explain  the  result?  The  strength  of  current 
in  the  two  cases  should  be  exactly  equal. 

EXPERIMENT  85. — Place  the  galvanometer  so  that  the 
needle  shall  come  to  rest  at  90°.  Now  send  the  current 
from  a  bichromate  cell  through  the  coil  connected  with 
the  B  terminals  and  then  without  making  other  changes 
reverse  the  direction  of  the  current  passing  through  the 
instrument.  Explain  the  action  of  the  needle  in  the  two 
cases  (T.  196). 


INDUCTION  CURRENT  INSTRUMENTS. 

(T.  228,  229,  230). 


The  induction  coil  is  an  instrument  designed  to  trans- 
form an  electric  current  of  a  low  electro-motive  force  to 
one  of  equivalent  energy  but  having  a  relatively  high 
electro-motive  force. 

There  are  three  quite  distinct  classes  of  induction 
coils  dirrering  in  construction  according  to  the  intensity 
of  current  desired  and  in  the  methods  of  regulating  and 
controlling  them. 

1.  The  first  type  is  a  very  large  coil  consisting  of  a 
primary  of  very  heavy  wire  designed  to  carry  strong  cur- 
rents   and   a   secondary   coil  consisting   of    thousands    of 
turns   of  very  fine  wire  very  carefully  insulated  in  which 
currents  having  thousands   and  even   millions  of  volts  of 
electro-motive  force  are  generated.      The  current  from  this 
class  of  coil   is   comparable  in   intensity   to   that   of    the 
static  machine.     They  are  used  in  various  kinds  of  scien- 
tific  research  and   more   recently   they   have   been    much 
employed  to  illuminate  Crookes   tubes  for  the  purpose  of 
producing  Roentgen  rays.      Some   of  the  larger  of    these 
coils  have  furnished  sparks  as  much  as  forty-two  inches 
in  length. 

2.  To    this  class  belong  the  coils  used    in    physio- 
logical research.      They  give  only  a  short  spark  but  admit 
of  a  wide  range  of  adjustment  for  modifying  the  character 
of  the  current.     They  are  constructed  so  as  to  permit  the 
secondary  coil  to  be  moved  over  the  primary.      They  are 
usually  spoken  of  as  Dubois-Reymond  coils. 

3.  To  this  class  belong  all  coils  used  in  therapeutical 


74  LABORATORY  MANUAL 

work  and  spoken  of  as  medical  induction  coils.  The  cur- 
rent is  practically  the  same  as  that  produced  by  those  of 
the  second  class  excpt  that  the  former  do  not  as  a  rule 
admit  of  so  wide  a  range  and  gradual  change  in  the 
strength  and  character  of  the  current.  Coils  of  this  form 
are  often  enclosed  in  a  neat  case  containing  a  small  bat- 
tery, conducting  cords,  electrodes,  etc.,  and  constitute  a 
-convenient  portable  instrument  for  the  physician's  use. 

THE    SIMPLE    LABORATORY    INDUCTION    COIL. 

This  instrument  consists  of  a  primary  coil  only,  the 
secondary  coil  being  absent.  It  has  sufficient  binding 
posts  to  attach  the  battery  to  it  and  electrodes  are  fur- 
nished through  which  the  induced  current  can  be  utilized. 
The  parts  are  simple  and  plainly  visible  in  order  that  the 
student  may  become  familiar  with  its  construction  and 
with  the  principles  involved  in  its  operation.  The  descrip- 
tion of  the  physician's  induction  coil  which  follows  in- 
cludes all  that  need  be  said  regarding  the  primary  coil 
and  its  currents. 

EXPERIMENT  86.  —Attach  a  4  volt  battery  to  the  sim- 
ple coil  and  adjust  the  parts  so  that  it  shall  be  properly 
•excited.  Study  the  mechanism  and  working  principles  of 
the  automatic  interrupter.  The  following  are  some  of  the 
points  to  which  the  student  should  give  his  attention: 

1.  Determine  the  various  points  for  attaching  elec- 
trodes for  applying  the  induced  current. 

2.  Determine  the  time  of  flow  and   the  direction  of 
the  induced  current,  i.  e. ,  whether  it  flows  at  the  "make" 
or  "break"  of  the  battery  current.      This  is  best  done  by 
slowly  moving  the  vibrator  backward  and  forward  by  hand 
and  passing  the  current  thus  induced  through  the  tongue. 

3.  Determine  how  the  soft  iron   core  becomes  mag- 


OF    ELECTROTHERAPEUTICS.  75 

metized  by  the  passage  of  the  battery  current.  From  the 
principles  of  electro-magnetic  induction  what  is  the 
direction  (compared  to  that  of  the  battery  current)  of  the 
induced  E.  M.  F.  when  the  core  is  becoming  magnetized 
.and  when  it  loses  its  magnetic  lines  of  force? 

4.  What  do  you  think  of  the  relative  rates  with 
which  the  core  takes  up  and  loses  its  magnetic  lines  of 
force?  What  is  the  effect  on  the  E.  M.  F.  of  the  primary 
induced  current  of  increasing  the  strength  of  the  battery 
current  through  the  coil? 

EXPERIMENT  87. — Test  for  the  effect  of  moving  the 
brass  tube  with  respect  to  the  iron  core  upon  the  E.  M.  F. 
of  the  primary  induced  current.  What  is  the  effect  where 
you  employ  a  tube  with  a  slit  along  its  entire  length?  Try 
the  effect  of  enclosing  the  primary  coil  in  a  cylinder  of 
metal  and  what  results  when  the  circuit  in  this  cylinder  is 
broken?  What  is  your  explanation  of  the  results  of  the 
above  observation  ? 

EXPERIMENT  88.  — Examine  the  electric  bell  and 
notice  the  general  similarity  of  its  construction  to  that  of 
the  interrupter  of  the  coil.  Notice  the  spark  produced  by 
the  extra  current.  Does  it  correspond  to  the  primary 
induced  current  of  the  coil?  At  what  points  would  you 
attach  electrodes  to  the  bell  in  order  to  send  the  current 
through  a  patient? 


THE  PHYSICIAN'S  INDUCTION  COIL. 

To  rightly  understand  the  therapeutic  capacities  of 
the  faradic  battery  or  physician's  induction  coil  it  is  neces- 
sary to  start  with  a  clear  conception  of  the  mechanism  by 
which  the  various  currents  derived  from  this  apparatus  are 
produced. 

The  analysis  of  one  of  the  simpler  forms  of  induction 
coil,  such  as  is  commonly  employed  by  physicians  will 
best  serve  this  purpose  as  it  contains  all  the  essential 
elements  entering  into  this  form  of  apparatus.  The  more 
elaborately  constructed  coils  are  but  attempts  to  perfect 
the  working  of  one  or  more  of  the  parts  of  which  these 
simpler  or  cheaper  coils  are  composed. 

The  induction  coil  apparatus  used  for  therapeutic 
purposes  must  have — 

A  primary  battery,  or  other  original  source  of  current, 

A  primary  coil, 

A  temporary  magnet, 

An  interrupter,  or  circuit-breaking  device, 

A  secondary  coil, 

Some  means  for  varying  the  amount  of  current 
induced  in  either  coil. 

Separate  consideration  will  be  given  to  each  of  these 
parts. 

The  Primary  Battery. — In  the  ordinary  portable 
faradic  battery  one  or  two  wet  or  dry  cells  furnish  the 
current  which  excites  the  induced  currents  in  the  coils. 
The  number  and  electro-motive  force  of  these  cells  must 
be  proportionate  to  the  resistance  to  be  met  with  in  the 
coil  circuits.  When  wet  cells  are  used  they  are  commonly 


OF    ELECTROTHERAPEUTICS.  77 

either  the  bichromate  or  ammonium  chloride  cells.  The 
electro-motive  force  of  the  former  (1.9)  is  about  one- 
fourth  higher  than  the  latter  (1.4),  neither  do  they  polarize 
so  quickly  and  therefore  maintain  a  more  constant  cur- 
rent. The  dry  cells  are  more  convenient  because  of 
being  dry,  but  they  cannot  be  renewed  by  the  operator 
but  must,  when  exhausted,  be  replaced  by  new  ones. 
The  composition  entering  into  the  various  dry  cells  is  a 
trade  secret,  but  those  of  larger  size  usually  have  zinc  and 
carbon  elements  with  a  paste  containing  ammonium 
chloride  as  an  excitant.  The  chloride  of  silver  dry  cell  is 
the  most  convenient  because  of  its  small  size — but  its 
electro-motive  force  (.9)  is  less  than  that  of  other  forms 
of  dry  cells.  It  requires  from  two  to  three  volts  pressure 
to  properly  energize  the  ordinary  induction  coil  apparatus, 
and  a  dynamo  current  can  be  used  to  furnish  this  current 
quite  as  well  as  a  primary  battery,  but  for  portable  bat- 
teries this  source  of  current  for  exciting  the  coils  cannot 
be  utilized.  With  coils  of  greater  resistance  more  electro- 
motive force  is  needed  in  the  circuit  from  which  the 
primary  energy  is  obtained,  and  in  case  primary  battery 
cells  are  used  to  supply  the  current  the  number  must  be 
sufficient  to  meet  the  requirements  of  increased  resistance. 
So  it  happens  that  in  certain  forms  of  induction  apparatus 
recently  put  upon  the  market,  in  which  the  secondary  coil 
contains  a  great  many  turns  of  very  fine  wire,  four  or 
more  primary  battery  cells  are  needed  to  properly  energize 
the  coils. 

The  Primary  Coil. — The  main  purpose  of  the 
primary  coil  is  to  furnish  a  path  for  the  battery  current 
and  to  interrupt  and  transform  that  current  in  such  a 
manner  as  to  create  induced  currents  in  a  secondary  coil 
which  is  either  wholly  or  but  partially  within  its  field  of 


78  LABORATORY  MANUAL 

influence.  To  accomplish  this  purpose  the  primary  coil; 
need  be  made  of  but  few  turns  of  a  comparatively  coarse 
wire;  the  main  object  being  to  offer  but  little  resistance  to- 
the  primary  battery  circuit.  Our  laboratory  experimental 
induction  coils  contain  three  turns  of  number  19  wire  in 
the  primary  coil,  the  outside  diameter  of  the  coil  being 
2  centimeters  and  its  length  10  centimeters.  There  is,  as 
we  shall  presently  see,  a  current  possessing  peculiar  physi- 
cal properties  induced  in  this  primary  coil,  which  is  utilized 
for  therapeutic  purposes  and  called  the  primary  current. 
For  the  purpose  of  giving  a  different  quality  to  this 
primary  current  some  manufacturers  have  increased  the 
number  of  turns  of  the  primary  coil  and  used  wire  of 
different  sizes.  The  battery  current  which  traverses  the 
primary  coil  has  for  a  part  of  its  course  a  vibrator  spring,. 
Fig-  35>  and  a  set  screw  and  post  which  form  very  essen- 
tial elements  in  the  action  of  the  induction  coil  apparatus 
as  will  be  seen  later. 

A  Temporary  Magnet. — A  soft  iron  bar  or  a  bun- 
dle of  soft  iron  wires  capable  of  being  readily  magnetized 
by  the  passage  of  the  battery  current  along  the  primary 
coil  and  again  promptly  losing  its  magnetism  as  this  bat- 
tery current  is  interrupted,  is  the  part  of  the  induction 
coil  apparatus  upon  which  its  action  chiefly  depends. 

The  main  purpose  of  the  temporary  magnet  is  to 
break  the  battery  circuit  and  so  interrupt  the  flow  of  cur- 
rent from  the  battery  through  the  primary  coil.  This  the 
temporary  magnet  does  the  instant  it  becomes  magnetized 
through  the  influence  of  the  current  passing  in  the  primary 
coil  which  is  wound  about  it.  By  its  magnetic  force  it 
attracts  the  iron  head  on  the  vibrator  spring  or  interrupter, 
Fig.  35,  and  draws  away  the  spring  from  the  point  of 
the  adjusting  screw  (G)  and  so  leaves  a  gap  (M)  in  the 


d 

^ 

P- 


;r 

-C 
<s>    , 

2  • 

i 

*n 


a 

Q 


8o 


LABORATORY  MANUAL 


battery  circuit.  This  stops  the  flow  of  the  battery  current 
in  the  primary  coil.  The  soft  iron  core  then  loses  its  mag- 
netism and  releases  the  head  of  the  vibrator  spring  which 
flies  back  and  is  again  in  contact  with  the  point  of  the 
adjusting  screw.  A  second  advantage  gained  by  the 
temporary  magnet,  if  placed,  as  it  is  in  many  of  the 
simple  forms  of  induction  apparatus  within  the  turns  of 
the  primary  coil,  is  an  augmenting  of  the  inductive  effect 

on  the  coils  by  reason 
of  the  magnetic  lines 
of  force  emanating 
from  the  magnet  and 
cutting  the  turns  of 
wire  in  the  primary 
and  secondary  coils. 
In  some  of  the  Du- 
bois-Reymond  forms 

Fig.  ?6.    Faradic  Coil  with  Dry  Cells.  of   induction  coil  the 

temporary  magnet  is  used  only  to  interrupt  the  circuit  of 
the  battery  current  and  is  placed  at  a  distance  from  the 
primary  and  secondary  coils  and  so  this  augmenting  in- 
ducing action  upon  them  is  lost. 

The  Circuit-breaker  or  Interrupter. — The  cur- 
rent that  flows  from  the  battery  through  the  primary  coil 
must  be  broken  or  interrupted  at  intervals,  since  it  is  by 
the  change  of  potential  in  the  circuit  that  is  thus  produced 
that  the  induced  currents  in  the  coils  are  created.  The 
range  of  frequency  of  such  interruptions  is  determined  by 
the  kind  of  device  that  is  used  for  producing  them.  In 
the  ordinary  coils  the  interruptions  are  effected  by  a  spring 
at  the  extremity  of  which  is  an  iron  head  ( H ),  Fig.  35.  This 
bit  of  iron  is  alternately  attracted  to  and  released  from  the 
temporary  magnet.  The  rapidity  with  which  interruptions 


OF    ELECTROTHERAPEUTICS.  8 1 

can  be  made  by  the  mechanism  varies  greatly  in  different 
instruments.     It  depends  upon  the  strength  of  the  mag- 
netic  flux,  the  readiness  with  which  the  magnet  takes  on 
and  gives  up  its  magnetism,  the  length  of  the  spring  and 
its  elasticity.     Seldom  are  any  two  instruments  of  the  same 
pattern  alike  in  all  of  these  particulars.     The  maximum 
of  interruptions  that  can  be  brought  about  in  our  ordinary 
laboratory  coils   averages   60   per  second,  and  these  are  a 
fair  sample   of    the   induction   coils  in  general  use.     By 
greater  attention  to  details  in  the  construction  of  this  and 
other  parts  of  the  induction  coil,  as  in  the  use  of  longer 
and   more   nicely    adjustable    springs,   and   the  use   of    a 
quality  of  iron  in  the  temporary  magnet  that  will  insure 
the   greatest   promptness    in    response    to    the    inductive 
influence,  the  rapidity  of  interruptions  by  this  method  can 
be  considerably  increased.     But  we  have  yet  failed  to  find 
an  instrument  with  a  spring  vibrator  in  which  the  number 
of   interruptions  can  be  made  to  reach   200   per  second. 
The  number  of  interruptions  in  an  induction  coil   current 
is  one  of   the  important  elements    in   producing   physio- 
logical   and   therapeutic    effects,   since    the   greater   their 
frequency  the  more  the  sharp  and  irritating  quality  of  the 
current   is    reduced,   and   the   more   soothing  it  is  in  its 
influence.     Numerous  attempts  have  been  made  to  secure 
more  rapid  and  uniform  interruptions   by   other   arrange- 
ments  than   that   of    the   spring  vibrator,  but  so   far   the 
devices   have   been  either  too   complex   or   expensive    to 
create  much  demand  for  them.     The  Englemann  segmented 
rotary  interrupter,  run  by  an  electric  motor,  is  capable  of 
greatly  increasing  the   number  of    interruptions  and  with 
perfect  uniformity,  but  its  cost  places  it  beyond  the  reach 
of  the  majority  of  those  using  induction  coils. 


82 


LABORATORY  MANUAL 


Fig.  37.    Form  of  Induction  Coil,  used  in  this 
Laboratory. 


The  Secondary  Coil.— The  secondary  coil  is  the 
induction  coil  proper,  and  the  current  derived  from  it  can 
be  caused  to  vary  considerably  in  strength  and  quality  at 

the  will  of  the  op- 
erator. This  coil  is 
always  made  of  finer 
wire  than  that  used 
in  the  primary  coil. 
It  usually  has  a  much 
greater  number  of 
turns  also  and  the 
length  of  the  wire  is, 
of  course,  propor- 
tionately increased. 
In  our  laboratory  ex- 
perimental coils  the 
secondary  is  wound 
with  number  31  wire  and  has  3  layers,  the  length  of  wire 
used  being  about  180  feet,  the  resistance  of  which  is  about 
35  ohms.  Most  secondary  coils  for  physicians'  use  are 
now  made  of  still  finer  wire.  Number  36  is  preferred  by 
many,  and  the  number  of  layers  is  as  many  as  eight  or  ten 
or  even  more. 

The  finer  the  wire  the  greater  the  number  of  turns 
made  in  each  layer,  and  as  each  additional  turn  of  wire 
adds  one  to  the  frequency  with  which  the  lines  of  magnetic 
force,  emanating  from  the  primary  coil  and  the  temporary 
magnet,  cut  the  secondary  coil,  and  so  increase  the  electro- 
motive force  of  the  secondary  coil  current,  a  great  number 
of  turns  in  the  secondary  coil  is  by  some  thought  desirable. 
But  there  is  a  limit  to  the  advantages  to  be  gained  by 
lenghtening  the  wire  and  increasing  the  number  of  turns 
in  the  secondary  coil.  The  resistance  of  the  amount  of 


OF   ELECTROTHERAPEUTICS.  83 

wire  used  and  of  the  self  induction  created  in  the  coil  may 
prove  too  much  for  the  primary  battery  current  to  over- 
come and  the  resulting  secondary  induced  current  will  be 
very  feeble. 

Much  of  the  efficiency  of  the  faradic  or  induction 
coil  apparatus  depends  upon  the  nature  of  the  secondary 
coil  current  and  as  a  different  quality  is  required  in  this 
current  for  different  therapeutic  purposes,  some  manu- 
facturers provide  several  secondary  coils  with  different 
sizes  and  turns  of  wire.  Others  make  a  continuous 
winding  of  the  one  size  of  wire  but  make  this  of  consid- 
erable length,  and  then  tap  the  wire  at  intervals  so  that 
the  current  from  all  or  only  a  part  of  the  coil  can  be  used 
as  desired.  The  nature  of  this  secondary  current  as  com- 
pared with  the  primary  induced  current  will  be  considered 
further  on. 

Current  Regulation. — Every  induction  coil  appara- 
tus is  provided  with  some  means  for  increasing  or  decreas- 
ing the  strength  of  the  currents  derived  from  it.  This  is 
done  by  modifying  the  strength  of  the  magnetic  field  that 
induces  currents  in  the  coils.  One  of  two  ways  is  used 
to  do  this.  The  coils  are  arranged,  in  the  one  case,  to  move 
one  over  the  other  as  in  the  Dubois-Reymond  type  of  coil, 
which  is  the  form  usually  employed  by  physiologists  for 
their  experimental  work,  and  which  produces  very  fine 
and  uniform  gradations  in  the  amount  of  current.  Or  a 
metal  shield  of  brass  is  made  to  slip  over  the  temporary 
magnet  placed  in  the  axis  of  the  coils  which  shield,  when 
in  place,  attracts  to  itself  the  lines  of  magnetic  force 
emanating  from  the  magnet  and  prevents  them  from 
cutting  across  the  turns  of  this  coil.  As  the  shield  is 
removed  the  lines  of  magnetic  force  are  released  and  thus 
induce  currents  in  the  coils  in  proportion  to  the  extent  to 


84  .  LABORATORY  MANUAL 

which  the  magnet  is  uncovered.  A  crude  method  of 
measuring  the  strength  of  induction  coil  currents  is  to 
attach  an  inch  or  meter  scale  to  the  apparatus  so  as  to 
measure  the  position  of  this  shield  at  any  moment  or  in 
the  other  case  the  extent  to  which  one  coil  covers  the 
other.  All  the  better  instruments  are  provided  with  such 
a  scale. 

NATURE    OF    THE    INDUCTION    COIL    CURRENTS. 

We  must  now,  in  order  to  judge  of  their  therapeutic 
applications,  study  the  modalities  of  the  electric  currents 
that  are  derived  from  the  physician's  induction  coil. 
When  this  apparatus  is  in  action,  it  is  capable  of  generat- 
ing three  distinct  currents. 

The  battery  current, 

The  primary  induced  current, 

The  secondary  induced  current. 

The  Battery  Current. — No  attempt  is  made  to  use 
the  battery  current  in  the  induction  coil  apparatus  for 
therapeutic  purposes.  Its  function  is  to  supply  an  electro- 
motive force  in  such  manner  as  to  create  magnetic  lines  of 
force  in  the  temporary  magnet  and  exercise  an  inductive 
influence  upon  the  coils.  In  order  to  effect  this  so  as  to 
secure  a  succession  of  induction  current  impulses,  the 
battery  current  must  be  interrupted  with  more  or  less 
frequency,  as  it  is  only  by  varying  the  number  of  lines  of 
force  that  cut  across  the  coils  that  an  induced  current  is 
created  in  them.  The  "make"  and  "break"  of  the  bat- 
tery current,  which  is  effected  by  the  interrupter,  is  an 
indispensable  feature,  therefore,  in  the  induction  coil 
apparatus.  And  the  frequency  with  which  these  inter- 
ruptions in  the  battery  current  take  place  determines,  im 
a  great  measure,  the  nature  and  physiological  and  thera- 


OF   ELECTROTHERAPEUTICS.  85 

peutic  effects  of  the  induced  currents  which  follow.  The 
battery  current  should  be  strong  enough  to  saturate  the 
temporary  magnet  with  a  magnetic  flux  and  to  successfully 
withstand  the  opposing  electro-motive  force  which  is 
created  by  self-induction  in  the  primary  and  secondary 
coils  when  their  circuits  are  closed.  The  larger  the 
temporary  magnet  and  the  greater  the  resistance  and  num. 
ber  of  turns  in  the  primary  and  secondary  coils,  the 
greater  will  need  to  be  the  electro-motive  force  of  the 


Fig.  38.    Induction  Coil  with  changeable  Vibrator. 

primary  battery  used  for  furnishing  this  battery  current. 
The  battery  current  (ABBBA')  in  Fig.  35,  is,  of  course,  a 
direct  or  galvanic  current,  that  is  a  uni-directional  current, 
but  it  is  interrupted  or  broken  as  often  as  the  spring  (H) 
is  carried  away  from  the  contact  (M).  The  E.M.F.  of  this 
current  depends  upon  the  kind  and  number  of  cells  used, 
and  the  amount  of  current  depends  upon  the  resistance  in 
the  circuit.  The  quantity  of  current  may  vary,  therefore, 
from  half  an  ampere  to  several  amperes,  according  to  the 
make-up  of  the  apparatus. 


86  LABORATORY  MANUAL 

The  Primary  Induced  Current. — At  the  moment 
the  magnetic  lines  of  force  which  emanate  from  the  tem- 
porary magnet  as  a  result  of  the  influence  of  the  battery 
current  begin  to  cut  the  turns  of  the  primary  coil,  an 
electro-motive  force  is  generated  by  them  in  the  primary 
coil,  which  is  opposed  to  the  flow  of  the  battery  current 
and  decreases  it.  When  the  battery  current  is  interrupted 
by  the  breaking  of  the  circuit  at  the  spring  vibrator,  the 
inductive  influence  of  this  current  on  the  temporary  mag- 
net ceases,  and  there  is  a  sudden  withdrawal  of  the  mag- 
netic lines  of  force  which  came  from  this  source. 

This  sudden  loss  of  potential  creates  an  induced  cur- 
rent in  the  primary  coil  which  has  the  same  direction  as  the 
battery  current,  but  as  the  battery  circuit  is  open  between  the 
contact  point  and  the  spring,  this  current  can  only  trav- 
erse that  circuit  by  leaping  the  air-gap,  which  it  does  at 
times  and  causes  the  spark  which  is  seen  at  this  point 
when  the  instrument  is  in  action.  If  another  circuit  is 
provided  for  this  current  that  is  induced  in  the  primary 
coil  at  the  "break"  of  the  battery  current,  then  this  in- 
duced current  at  the  "break"  can  be  utilized  in  thera- 
peutic work.  And  this  is  the  origin  of  the  current  derived 
from  the  medical  induction  coil  that  goes  by  the  name  of 
primary  current.  It  is  a  unidirectional  current, (Fig.  39) 
but  interrupted  with  a  frequency  corresponding  to  the  move- 
ments of  the  vibrator.  It  has  the  same  direction  as  the 
battery  current,  but  differs  from  it  in  having  less  of  quantity 
but  higher  electro-motive  force.  Both  its  strength  and 
electro-motive  force  can  be  varied  by  moving  the  shield 
covering  the  core,  or  by  changing  the  position  of  the  core 
itself,  if  this  is  made  movable. 

The  primary  induced  current  has  in  a  feeble  way  the 
properties  of  a  direct  or  galvanic  current.  It  is  both  elec- 


OF    ELECTROTHERAPEUTICS.  87 

trolytic  and  cataphoric  to  a  slight  degree,  but  its  chief 
action  upon  the  living  organism  is  as  an  excitant  to  con- 
tractile tissue  and  to  sensory  nerves  by  reason  of  the  inter- 
ruptions which  cause  a  sudden  variation  in  potential.  The 
suddenness  of  this  change  in  electro-motive  force  makes 
this  current  a  powerful  stimulant  for  exciting  muscular 
contractions  and  for  arousing  the  action  of  sensory  nerves. 
The  Secondary  Induced  Current. — The  secondary 
coilwinding(FFFF)(Fig.  35)  w«r/Vm 

is  entirely  distinct  from  the  j.c*****  <?*"* 

TTto  7>trZu.e.tiot*, 

primary  and  has  its  separate 

terminals     at    the    binding-  °  o          *•          * 

posts  (EE').    In  some  forms  /g 

of  induction  coils  the  secon-         IL, 

».W4.'!  .-..of 

dary  coil  can  be  removed 
from  the  instrument,  and 
these  instruments  are  sup- 
plied with  several  secondary 
coils  differing  in  size  and 
length  of  wire  and  in  the  s»<*«aiajjy  •****«« 

number  of  turns.      There  are 

induced  currents  generated  in  the  secondary  coil  both  at 
the  "make"  and  "break"  of  the  battery  current.  The 
inductive  effect  on  the  turns  of  the  seconday  coil  at  the 
"make"  of  the  battery  current  is  due  to  the  lines  of  force 
from  the  magnet  cutting  across  them.  This  current  is  com- 
paratively slow  in  its  increase  to  the  highest  potential  be- 
cause of  the  somewhat  gradual  development  of  these  lines 
of  force.  The  induced  current  at  the  "break"  on  the  con- 
trary because  of  the  sudden  withdrawal  of  these  magnetic 
lines  of  force,  is  more  promptly  developed  to  its  greatest  in- 
tensity and,  of  course,  in  the  opposite  direction  from  the  cur- 
rent induced  at  the  "  make."  The  secondary  coil  current 


88  LABORATORY  MANUAL 

then  is  a  to  and  fro,  or  alternating  current  (Fig.  39)  with  the 
"break"  a  little  greater  in  intensity  but  shorter  in  dura- 
tion than  the  "make"  current,  while  the  frequency  of  the 
alternations  or  the  number  of  periods  depends  upon  the 
action  of  the  vibrator  or  interrupter.  The  electro-motive 
force  in  this  current  is  determined  by  the  number  of  turns 
in  the  coil  that  are  cut  by  the  magnetic  lines  of  force,  and 
the  quantity  of  current  is  determined  by  the  resistance 
offered  to  its  flow  and  the  strength  of  the  magnetic  flux 
which  induces  it.  The  electro-motive  force,  when  a  fine 
wire  of  many  turns  is  used  in  the  secondary  coil,  is  much 
higher  than  that  of  the  primary  induced  current,  while  the 
amount  of  current  is  correspondingly  much  less. 

The  alternating  character  of  this  current  prevents  it 
from  being  either  electrolytic  or  cataphoric,  while  its 
physiological  effects  depend  very  much  upon  the  struc- 
ture of  the  coil  and  the  frequency  of  the  alternations. 
If  the  alternations  are  very  frequent  and  the  coil  com- 
posed of  many  turns  of  fine  wire,  the  resulting  current, 
though  interrupted,  begins  to  resemble  in  physical  pro- 
perties a  sinusoidal  current.  The  approaches  to  and 
departures  from  the  highest  and  lowest  potential  in  each 
period  is,  by  this  construction,  made  more  gradual  and 
the  effect  physiologically  is  stimulating  and  yet  not  irritat- 
ing. Its  effect,  therefore,  is  tonic  and  at  the  same  time 
sedative  on  both  motor  and  sensory  nerves. 

EXPERIMENTS    WITH    THE    MEDICAL    INDUCTION    COIL. 

Before  proceeding  with  the  following  experiments 
demonstrate  the  induction  coil  to  the  instructor  in  charge 
of  the  laboratory. 

EXPERIMENT  89. — What  currents  does  the  physician's 
induction  coil  furnish?  Test  the  effect  of  removing  the 


OF    ELECTROTHERAPEUTICS.  89 

draw-tube.  What  are  the  effects  of  increasing  the  battery 
power?  Pass  the  current  through  the  body  from  arm  to 
arm.  Bare  the  fore-arm  and  with  pointed  electrodes  cov- 
ered with  absorbent  cotton  and  moistened  with  a  saline 
solution  and  with  the  other  flat  electrode  on  the  back  of 
the  neck,  cause  contractions  of  each  separate  muscle  of 
the  fore-arm  with  the  weakest  primary  and  then  with  the 
weakest  secondary  current  that  will  cause  a  contraction. 
The  pointed  electrode  should  be  placed  over  the  point  of 
entrance  of  the  nerve  supplying  the  muscle. 

EXPERIMENT  90. — Determine  by  moving  the  vibrator 
slowly  back  and  forth  whether  the  secondary  current  flows 
both  at  the  "make"  and  "break"  of  the  battery  current. 
Is  there  any  difference  in  the  direction  and  intensity  of 
the  impulses  ? 

EXPERIMENT  91. — Send  the  secondary  current  through 
the  galvanometer  which  is  considerably  removed  from  the 
coil,  and  notice  if  it  causes  any  deflection  of  the  needle. 
Move  the  interrupter  slowly  by  hand  and  see  if  there  is 
any  difference.  Determine  by  experiment  whether  either 
the  primary  or  secondary  induced  currents  are  capable  of 
effecting  electrolysis. 

EXPERIMENT  92. — Using  the  large  dissected  coil? 
study  the  effects  of  removing  the  secondary  coil  from  the 
primary  and  also  the  effect  of  varying  the  number  of  wires 
which  make  up  the  coil. 

EXPERIMENT  93. — With  the  skeleton  coil  and  a  tele- 
phone receiver  notice  the  induction  effect  between  two 
simple  coils.  Observe  the  sounds  on  making  and  breaking 
the  circuit  slowly  and  the  effect  of  removing  the  core. 


THE  MAGNETO-ELECTRIC  MACHINE. 

(T.    222,    223,    224,    461.) 


The  magneto-electric  machine  is  a  current  generator 
which  was  at  one  time  quite  generally  used  in  therapeutics. 
The  form  commonly  employed  consists  of  two  coils  of 
fine  wire,  each  having  a  soft  iron  core  and  mounted  in 
such  a  manner  that  they  can  be  rotated  near  a  permanent 
horse-shoe  magnet.  In  this  manner  the  number  of  mag- 
netic lines  of  force  passing  through  the  two  cores  is  made 
to  change  continually,  their  polarity  also  changing,  and 
corresponding  currents  are  set  up  in  the  coils  according 
to  the  principles  discovered  by  Faraday.  The  two  coils 
are  so  joined  that  the  E.  M.  F.  generated  in  each  re- 
enforces  the  other.  In  machines  not  employing  a  com- 
mutator the  current  is  alternating  in  nature,  each  rev- 
olution of  the  coils  corresponding  to  a  single  impulse 
in  each  direction.  The  rate  of  alternation  is  consider- 
ably slower  than  in  the  secondary  induction  coil  current 
and  in  the  sinusoidal  current.  The  variations  of  E.  M.  F. 
are  not  so  abrupt  as  in  the  induction  coil  although  some 
types  are  so  constructed  as  to  cause  sudden  variations 
of  the  E.  M.  F.  The  current  from  the  magneto-electric 
generator  may  be  represented  graphically  very  much  like 
the  sinusoidal  current  except  that  the  undulations  are  much 
less  regular.  In  some  machines  of  this  kind  the  current  is 
made  to  flow  all  in  one  direction  by  means  of  a  commuta- 
tor. The  current  then  resembles  the  direct  or  galvanic 
current  except  that  it  is  irregular  both  as  to  amount  of 
current  and  electro-motive  force. 


OF    ELECTROTHERAPEUTICS.  9!       . 

EXPERIMENT  94. — Examine  the  various  forms  of 
magneto-electric  generators  in  the  laboratory  and  be  pre- 
pared to  demonstrate  any  of  them  to  the  instructor.  Take 
the  current  from  one  of  them  through  your  body  from 
hand  to  hand  and  compare  the  sensation  to  that  produced 
by  the  direct  current  (galvanic)  and  the  induced  current 
from  the  induction  coil  (Faradic).  Attempt  to  electrolize 
a  solution  of  copper  sulphate  with  it.  Determine  the 
nature  of  the  current  by  passing  it  through  the  long  coil 
of  your  galvanometer.  How  can  the  current  be  regulated 
in  strength  ?  Is  the  current  generated  sufficient  to  heat  a 
cautery  wire?  Can  it  be  used  for  cataphoric  or  electro- 
lytic purposes  on  the  body? 


THE  SINUSOIDAL  CURRENT. 


By  a  sinusoidal  current  is  meant  an  alternating  induced 
current  in  which  not  only  the  rise  and  fall  of  potential  or 
electro-motive  force  of  positive  direction  is  immediately 
succeeded,  without  break,  by  an  exactly  corresponding 
rise  and  fall  of  potential  of  negative  direction,  but  one  in 
which  this  rise  and  fall  in  both  directions  would,  if  shown 
with  accuracy  in  diagram,  describe  a  sine  curve.  The 
accompanying  illustration,  Fig.  40,  taken  from  Prof.  H.  S. 
Carhart's  work  on  Elementary  Physics,  with  the  permission, 
of  the  author,  well  illustrates  this  form  of  curve. 

Mathematically  considered  this  curve  may  be  defined 
as  one  resulting  from  two  rectilinear  motions  at  right 
angles  to  each  other;  the  one  being  a  uniform  rectilinear, 
the  other  a  simple  harmonic  motion.  This  last  named 
motion  is  one  well  illustrated  by  the  common  pendulum, 
which  moves  most  rapidly  at  the  middle  of  its  swing,. 


«92  LABORATORY  MANUAL 

•decreasing  in  -rapidity  as  it  approaches  the  ends.  The 
figure  represents  diagramatically  a  combination  of  these 
two  motions.  The  equal  spaces  made  by  the  vertical  lines 
at  the  right  represent  the  progress  of  the  uniform  rectilinear 
movement  from  left  to  right,  while  the  spaces  between  the 
horizontal  lines  represent  the  simple  harmonic  movement 
or  sine  displacements.  These  spaces  on  the  vertical  lines 
are  obtained  by  dividing  the  circle  at  the  left  into  16  equal 
-arcs  and  drawing  horizontal  lines  through  the  points 
marking  their  boundaries,  as  i,  2,  3,  etc.  Now  if  we 
assume  that  this  circle  is  made  to  revolve  at  right  angles 


10  p^gj 

i, 

\ 

N 

5 

7 

/\       \      *      '      xN. 

\ 

1 

\ 

/ 

V 

\\J    '     *'     \i 

1 

\ 

/ 

\ 

w  i- 

d 

\ 

1 

\ 

1 

\| 

L-<*:-,l 

* 

\ 

1 

\ 

/ 

f 

\ 

J 

\ 

1 

»Sl  7          \^S 

.'/ 

v 

> 

\ 

/ 

10—g-^ 

.. 

n 

?. 

n 

jj 

' 

Fig.  40. 

to  the  plane  of  the  paper  with  the  line  o,  5,  e,  for  its  axis, 
one  revolution  of  the  circle  will  correspond  to  a  complete 
vibration  of  a  pendulum,  and  if,  while  revolving,  the 
•circle  moves  from  left  to  right  at  a  uniform  rate  along 
the  axis  o,  5,  e,  then  the  displacement  of  any  point  upon 
the  margin  of  the  circle  from  the  middle  line  is  propor- 
tioned to  the  sine  of  the  angle  of  rotation  on  the  circle. 
Thus  if  we  take  the  point  5  and  rotate  it  through  the  arc 
5,  6,  the  vertical  displacement  of  the  point  5  will  be  the 
sine  of  the  angle  of  rotation  5,  o,  6.  Again  the  vertical 
displacement  from  5  to  7  is  the  sine  of  the  angle  5,  o,  7. 
It  will  be  seen  that  these  sines  correspond  to  vertical  dis- 
tances between  the  horizontal  lines  at  the  right  of  the 


OF   ELECTROTHERAPEUTICS,.  93' 

circle  and  that  the  diagonal  lines  in  the  parallelograms  are- 
but  the  resultant  of  these  two  movements  of  the  circle. 

The  sine  curve  can  be   platted  by  completing  these 
diagonal  lines  through  one  entire  revolution  of  the  circle. 

The  current  derived  from  the  secondary  circuit  of  am 
induction  coil,  Fig.  35,  has  been  shown  to  be  alternating, 
but  the  positive  and  negative  alternations  differ  considera- 
bly in  electro-motive  force  and  the  gradations  from  zero 
to  the  greatest  difference  of  potential  in  either  direction 
are  not  regular  and  uniform  but  quite  the  contrary. 
Moreover,  the  secondary  current  of  the  induction  coil  is 
interrupted,  the  time  interval  occupied  by  the  interruptions 
exceeding  considerably  that  consumed  by  the  passage  of 
the  current.  In  these  respects  the  secondary  current  of 
the  induction  coil  differs  from  a  sinusoidal  alternating 
current  in  its  physical  properties,  and  these  physical  differ- 
ences have  of  necessity  a  corresponding  difference  in 
physiological  and  therapeutic  effects.  By  increasing  the 
length  and  number  of  turns  of  the  secondary  coil  and 
increasing  the  rapidity  of  the  vibrations  of  the  interrupter 
the  current  derived  from  the  secondary  coil  of  the  induc- 
tion apparatus  is  made  to  approach  more  nearly  in  physical 
and  physiological  properties  the  sinusoidal  current  as  at 
present  used. 

The  magneto-electric  apparatus,  which  has  been 
spoken  of  and  which  some  years  ago  was  not  infrequently 
seen  in  physicians'  offices,  likewise  creates  an  alternating 
current.  But  the  alternating  current  generated  by  this- 
little  machine,  while  it  shows  no  interruptions  when  the- 
coils  are  revolving,  is  yet  quite  irregular  as  compared 
with  a  sinusoidal  current,,  since  the  lines  of  magnetic- 
force  emanating  from  the  poles  of  the  magnet  cut  the- 
turns  of  wire  in  the  coils  as.  they  revolve,  in  such  manner 


94  LABORATORY  MANUAL 

as  to  create  no  uniformity  in  the  increase  and  decrease  of 
the  induced  currents.  It  is,  however,  only  in  this  feature 
of  construction  that  this  well-known  magneto-electric 
machine  differs  from  several  of  the  sinusoidal  machines 
that  are  now  being  manufactured  for  therapeutic  work. 
In  these  latter  the  attempt  is  made,  with  more  or  less 
success,  to  secure  such  uniformity  in  the  increase  and 
decrease  of  the  number  of  the  magnetic  lines  of  force 
that  cut  the  coils  as  they  revolve,  that  the  electro-motive 
force  generated  will  describe  the  sine  curve.  This  desir- 
able result  is  the  more  nearly  attained  according  as  the 
permanent  or  electro-magnets  used  are  so  shaped  as  to 
furnish  to  the  coils  a  strictly  uniform  gradation  in  the 
strength  of  the  magnetic  field  as  they  enter  and  leave  it. 
Although  the  modern  apparatus  shows  great  progress  in 
skill  and  workmanship  yet  it  is  quite  probable  that  no  so- 
called  sinusoidal  machine  has  yet  been  constructed  that 
describes  accurately  in  its  action  the  sine  curve. 

The  alternating  current  dynamos  now  used  so  exten- 
sively for  lighting  incandescent  lamps  furnish  a  current 
which  is  roughly  sinusoidal  and  can  be  utilized  by  physi- 
cians who  have  access  to  it  and  have  some  form  of  con- 
troller suitable  for  modifying  its  strength  and  voltage.  As 
the  speed  of  these  dynamos,  while  in  action,  is  quite 
uniform,  the  number  of  alternations  do  not  vary  much 
and  the  frequency  is  often  much  less  than  is  wanted  in 
therapeutic  work,  being  often  but  124  alternations  per 
second.  It  is  convenient  and  oftentimes  quite  desirable 
to  have  an  apparatus  for  the  generation  of  a  sinusoidal 
current  so  arranged  that  the  operator  can  vary  the  fre- 
quency of  alternations,  the  electro-motive  force  and  the 
current  at  will,  and  this  is  possible  with  some  of  the 
machines  now  manufactured,  two  forms  of  which  will  be 
illustrated  and  described. 


OF    ELECTROTHERAPEUTICS.  95 

PHYSIOLOGY    AND    THERAPEUTICS   OF  THE    SINUSOIDAL 
CURRENT. 

There  are  several  physical  peculiarities  possessed  by 
the  sinusoidal  current  which  help  to  make  its  action  on 
the  body  different  from  that  of  other  forms  of  current. 
As  has  been  seen  from  the  foregoing  description  the 
increase  and  decrease  of  potential  in  this  form  of  current 
is  gradual  and  uniform  and  never  abrupt  nor  sudden  in 
its  change.  It  is  no  doubt  to  this  feature  of  the  current 
that  its  peculiar  action  on  the  sensory  and  motor  nerves  is 
mainly  due.  The  sensory  and  motor  mechanism  of  the 
body  is  capable  of  adjusting  itself  to  a  considerable  range 
of  difference  in  external  conditions  without  serious  dis- 
turbance or  discomfort,  provided  the  change  is  not  too 
sudden  or  violent.  Even  though  there  may  be  many 
periods  of  alternation  of  current  per  second  and  the 
electro-motive  force  be  quite  high,  yet  the  action  of  nerve 
and  muscle  is  still  capable  of  responding  to  such  varia- 
tions without  disagreeable  reaction  provided  the  change  in 
strength  is  gradual.  The  number  of  alternations  per 
second,  the  degree  of  electro-motive  force  and  the  quan- 
tity of  current  are,  no  doubt,  each  important  factors  in 
determining  the  physiological  and  therapeutic  effects  of 
this  current,  but  these  are  not  so  peculiar  to  it  as  is  this 
feature  of  uniformity  in  change.  The  effect  of  this  spe- 
cial feature  of  the  sinusoidal  current  is  to  lessen  the 
disagreeable  effects  of  electric  excitations  both  on  the 
sensory  and  motor  mechanism.  The  same  amount  of 
stimulation  to  muscular  action  can  be  aroused  as  by  any 
other  equally  powerful  means,  without  the  accompanying 
pain  and  consequently  without  the  shrinking  and  appre- 
hensiveness  on  the  part  of  the  patient  which  other  forms 
of  excitation  arouse.  In  this  lies  the  chief  advantage  of 


96  LABORATORY  MANUAL 

the  sinusoidal  current  over  the  current  derived  from  the 
secondary  induction  coil,  while  in  many  other  respects 
these  currents  are  similar  in  action. 

For  exciting  to  vigorous  action  muscular  tissue, 
therefore,  whether  it  be  the  voluntary  or  involuntary 
variety  of  muscle,  the  sinusoidal  is  the  current  par  excel- 
lence. Such  frequency  of  alternations  can  be  used  as  will 
adapt  the  excitation  to  the  requirements  of  the  muscular 
structure.  The  comparative  painlessness  of  the  applica- 
tions permits  the  use  of  greater  electro-motive  force  and 
more  current  than  can  be  used  either  from  the  induction 
coil  or  the  primary  battery,  so  that  physiological  action 
of  the  muscles  is  more  thoroughly  aroused  than  by  the 
use  of  either  of  these  other  forms.  The  more  nearly  the 
curve  of  current  conforms  to  the  sinusoidal  the  less  will 
there  be  of  effects  resulting  from  polar  action.  Electro- 
lysis and  cataphoresis  will  be  avoided  and  the  changes 
brought  about  in  the  tissues  to  which  the  current  is 
applied  will  be  mainly  those  which  are  normal  to  their 
function;  the  effect  of  the  current  being  to  arouse  that 
function  to  greater  activity.  When  we  consider  how 
many  of  the  normal  processes  of  the  body,  such  as  assim- 
ilation, circulation,  secretion,  excretion,  locomotion,  etc., 
depend  directly  upon  muscular  tone  and  vigor  it  will  be 
seen  at  a  glance  what  a  wide  range  of  therapeutic  applica- 
tion is  possessed  by  this  form  of  current  in  the  field  of 
muscular  excitation  alone.  It  has  been  highly  spoken  of 
by  many  competent  electro-therapeutists  as  a  means  of 
improving  the  nutrition  and  growth  of  muscular  tissue 
whenever  it  is  failing  from  lack  of  proper  excitation. 

General  muscular  weakness,  local  paralysis  or  paresis, 
lack  of  intestinal  peristalsis,  vaginal  and  rectal  prolapsus, 
due  in  whole  or  in  part  to  lack  of  muscular  tone,  and 


OF    ELECTROTHERAPEUTICS.  97 

vasomotor  debility  are  some  of  the   conditions  in  which 
this  form  of  current  has  proved  especially  beneficial. 

It  has  been  said  that  the  sinusoidal  current  is  remark- 
able for  the  little  amount  of  sensory  excitation  it  causes, 
and  so  permits  powerful  muscular  contractions  without 
discomfort.  Further  than  this  it  serves  to  allay  pain.  It 
is  as  much  if  not  more  serviceable  in  this  way  than  is  the 
current  derived  from  the  secondary  induction  coil  of  many 
turns.  Apostoli  and  others  have  borne  strong  testimony 
to  the  fact  that  the  greatest  success  they  have  attained 
with  this  form  of  current  has  been  in  allaying  the  pains 
that  occur  in  connection  with  the  pelvic  organs.  The 
pains  caused  by  uterine  inflammation,  pelvic  cellulitis, 
ovaritis,  salpingitis  and  congestion  are  quickly  allayed  by 
it.  Neuralgic  pains  are  relieved  and  those  of  spinal  irri- 
tation. Marked  effects  on  tissue  metabolism  have  been 
noticed  also  as  indicated  by  increased  consumption  of 
oxygen  and  more  rapid  elimination  of  carbon  dioxide. 
These  effects  are  in  all  probability  secondary  to  and 
dependent  upon  the  increased  muscular  activity  and 
analgesic  influence  of  the  current. 

THE    Me  INTOSH    SINUSOIDAL    APPARATUS. 

This  instrument,  Fig,  41,  is  one  result  of  the  most 
recent  attempts  by  manufacturers  to  provide  a  source  of 
sinusoidal  current  for  therapeutic  work.  It  consists  of  a 
small  motor  wound  for  the  no  direct  current  and  has  con- 
nected with  it  a  special  rheostat  for  controlling  its  speed. 
The  shaft  of  the  motor  is  extended  and  carries  on  this 
extension  the  armature  of  the  sinusoidal  machine,  thus 
making  a  very  convenient  and  compact  arrangement, 
doing  away  with  belts  and  pulleys.  The  armature  carry- 
ing the  winding  of  the  coils  of  wire  in  which  the  induced 


98 


LABORATORY  MANUAL 


sinusoidal  currents  are  generated  revolves  between  the 
poles  of  a  group  of  three  powerful  permanent  magnets, 
the  pole  pieces  of  which  are  so  shaped  as  to  secure  a 
uniform  gradation  in  the  lines  of  force  which  cut  across 
the  revolving  coils  on  the  armature.  From  the  coils  the 
current  is  conveyed  to  binding  posts  on  the  base  of  the 
instrument,  but  before  the  current  reaches  the  binding 
posts  a  graphite  rheostat  is  interposed  regulating  the 


Fig.  41. 

strength  of  the  current.  This  arrangement  makes  the 
apparatus  complete  It  is  only  necessary  to  connect  the 
binding  posts  on  the  top  of  the  motor  with  a  suitable 
direct  current  circuit  such  as  the  Edison  incandescent 
light  circuit,  or  a  street  car  or  power  dynamo  circuit  of 
higher  voltage,  provided  sufficient  lamp  resistance  is 
introduced  so  as  to  reduce  the  potential,  and  then  com- 
plete the  patient's  circuit  by  attaching  electrodes  to  the 
binding  posts  on  the  base.  The  rapidity  of  alternations 
and  consequently  the  voltage  is  readily  modified  by  the 


OF    ELECTROTHERAPEUTICS.  99 

rheostat  in  the  motor  circuit  while  the  strength  of  current 
can  be  graduated  independently  by  means  of  the  rheostat 
in  the  patient's  circuit.  Two  additional  brushes  are  in 
contact  with  a  commutator  on  the  outer  end  of  the  arma- 
ture shaft  and  these  serve  to  deliver  the  current  generated 
as  a  current  in  one  direction,  instead  of  an  alternating 
one,  when  this  is  desired.  The  direct  current  so  produced 
can  be  thrown  into  the  patient's  circuit  by  a  proper  move- 
ment of  a  switch  which  is  provided  on  the  base.  By 
connecting  the  motor  of  this  instrument  with  a  power  cir- 
cuit in  this  laboratory,  the  current  supplied  to  the  motor 
registering  by  a  Weston  meter  120  volts,  we  were  able  to 
run  the  armature  shaft  at  the  speed  of  5280  revolutions 
per  minute  when  all  resistance  was  off  the  motor  circuit. 
The  number  of  alternations  would  of  course  be  twice  this, 
or  10560  per  minute;  or  176  per  second.  By  diminishing 
the  speed  of  the  motor  any  less  number  of  alternations 
per  second  could  be  obtained.  The  strength  of  current 
could  be  modified  from  that  which  was  barely  perceptible 
up  to  that  which  would  produce  the  most  powerful  muscu- 
lar contractions,  and  yet  at  no  time  was  the  sensation  pro- 
duced, either  in  the  integument  or  muscles,  disagreeable 
or  painful  as  is  so  often  the  case  with  the  current  from  the 
faradic  coils.  The  electro-motive  force  that  is  developed  in 
the  patient's  circuit  depends  upon  the  speed  with  which  the 
armature  is  made  to  revolve.  At  the  highest  speed  attain- 
able the  Weston  alternating  voltmeter  registered  no  volts 
and  at  the  slowest  speed,  33  volts.  If  a  lower  electro- 
motive force  with  great  frequency  of  alternations  is  desired 
this  could  be  readily  accomplished  by  having  a  less  num- 
ber of  turns  in  the  armature  winding. 

The  direct  or  galvanic  current  that  is  furnished  by  this 
instrument  is  of  course  not  uniform  in  potential  but  varies 


100  LABORATORY  MANUAL 

in  intensity  at  each  revolution  of  the  armature.  With  this 
also  the  speed  determines  the  amount  of  current.  The 
milliampere-meter  showed  this  current  to  be  10  milliam- 
peres  at  high  speed,  and  when  a  patient  was  between  the 
electrodes  and  the  direct  current  was  carried  up  to  the 
limit  of  tolerance  the  amount  of  current  was  between 
three  and  four  milliamperes.  Electrolytic  work  was 
readily  done  by  the  direct  current  but  the  comparatively 
high  electro-motive  force  that  was  required  to  get  sufficient 
current  for  electrolysis  might  in  some  instances  in  actual 
practice  prove  disagreeable  to  a  patient,  and  the  direct 
current  derived  from  this  apparatus  cannot  be  made  to 
take  the  place  entirely  of  a  galvanic  battery  or  other 
sources  of  direct  current. 

THE    KENNELLY    SINUSOIDAL    MACHINE. 

This  machine  (Fig.  42 )  bears  a  striking  resemblance  to 
the  ordinary  multi-polar  alternating  current  dynamo,  but  on 
closer  examination  it  will  be  found  that  both  the  primary 
(exciting)  and  the  secondary  windings  are  placed  upon  the 
field  frame.  The  field  frame  is  of  laminated  iron  sup- 
ported by  castings  and  has  twelve  poles;  on  each  pole  is  a 
spool  with  two  windings  of  wire.  The  inner  has  eight 
layers  of  fine  wire  and  the  outer  two  layers  of  coarse  wire. 
All  the  coarse  wire  windings  are  connected  in  series  in 
such  a  way  that  the  magnetic  polarity  produced  shall  be 
alternately  north  seeking  and  south  seeking,  when  a  direct 
current  is  sent  through  this  circuit. 

The  armature  is  composed  of  several  discs  of  sheet 
iron  firmly  fastened  together,  having  slots  and  projections 
as  will  be  seen  from  the  figure.  This  armature  is  just 
large  enough  to  rotate  freely  within  the  concentrically 
arranged  pole  pieces.  Bearing  in  mind  the  relation  of  the 


OF    ELECTROTHERAPEUTICS. 


IOI 


secondary  coil  to  the  pole,  it  is  evident  that  anything 
causing  an  increase  or  decrease  of  magnetic  lines  of  force 
through  the  pole,  /'.  e.,  any  variation  of  the  magnetic  flux, 
will  induce  a  current  of  electricity  in  the  secondary.  The 
E.  M.  F.  of  this  induced  current  will  depend  upon  the 
number  of  turns  of  wire  and  the  rate  of  increase  or 
decrease  of  the  magnetic  flux.  In  this  machine  the  direct 


Fig.  42. 

current  passing  through  the  coarse  wire  windings  consti- 
tutes the  magneto-motive  force;  this  remaining  constant, 
the  magnetic  flux  will  vary  inversely  with  the  reluctance, 
/.  e.,  the  "magnetic  resistance." 

The  law  of   the   magnetic  circuit  may  be  stated   as 

follows: 

magneto-motive  force 

magnetic    flux   =  — - 

reluctance. 

The  reluctance  of  air  being  very  great  as   compared 
with  that  of  iron  it  follows  that  the  magnetic  flux  in  any  pole 


102  LABORATORY  MANUAL 

will  be  suddenly  increased  when  the  air-gap  or  slot  oppo- 
site that  pole  is  displaced  by  the  iron  projection  of  the 
rotating  armature,  thus  inducing  a  current  in  one  direction 
and  the  next  instant  when  the  wire  projection  is  passing 
and  the  next  slot  is  coming  opposite  the  pole  there  will  be 
a  decrease  of  magnetic  flux  and  a  corresponding  current 
in  the  opposite  direction. 

The  slots  and  projections  of  the  armature  are  so 
proportioned  that  the  graphic  representation  of  these 
alternations  of  the  current  closely  approximate  the  true  sine 
curve,  thus  giving  the  so-called  sinusoidal  current. 
Twenty-four  alternations  or  twelve  complete  periods  occur 
at  each  revolution  of  the  armature;  a  speed  of  80  revolu- 
tions can  be  attained  and  will  therefore  give  1920  alterna- 
tions per  second  or  a  frequency  of  960. 

The  E.  M.  F.  of  the  secondary  current  varies  with 
the  amount  of  current  flowing  in  the  primary,  /.  <?.,  with 
the  magneto-motive  force.  This  fact  offers  a  convenient 
method  for  regulating  the  voltage  of  the  secondary  with- 
out varying  the  speed.  The  primary  current  may  be 
derived  from  primary  batteries  or  from  street  mains  and 
should  be  passed  through  a  rheostat  so  that  it  may  be 
varied  from  two  amperes  to  the  small  fractional  part  of 
an  ampere. 

The  E.  M.  F.  when  the  secondary  is  open  varies 
directly  with  the  speed  and  the  strength  of  current  in  the 
primary  circuit.  With  one  ampexe  in  the  latter  circuit, 
the  limit  of  E.  M.  F.  in  the  secondary  is  about  50  volts, 
which  is  about  70  volts  at  the  top  of  each  wave,  the  50 
volts  representing  the  average  electric  pressure.  On  short 
circuiting  the  secondary,  the  voltage  is  reduced  nearly  to 
zero,  but  in  practice  this  will  not  occur  except  by  accident. 
The  E.  M.  F.  of  the  secondary  passing  through  the  body 


OF    ELECTROTHERAPEUTICS.  103 

of  a  patient  will  vary  with  the  resistance  offered,  but 
since  this  resistance  is  always  comparatively  high  the 
E.  M.  F.  will  practically  amount  to  that  recorded  by  a 
voltmeter  in  open  circuit. 

In  comparing  this  machine  with  others  built  for  the 
same  purpose  the  following  are  some  of  the  facts  to  be 
considered: 

The  Kennelly  machine  requires  both  a  motor  for 
running  and  some  independent  source  of  direct  current 
for  exciting  the  fields.  Neither  of  these  are  necessarily 
disadvantages  as  the  physician  may  possess  these 
accessories,  and  if  he  should  not  they  may  be  procured  at 
a  cost  probably  not  exceeding  that  of  those  furnished  with 
other  machines.  Further,  as  has  been  shown,  the  inde- 
pendent exciting  current  can  be  so  controlled  as  to  vary 
the  E.  M.  F.  of  the  secondary  without  affecting  the  rate 
of  alternations.  This  is  a  decided  advantage  and  one  not 
possessed  by  some  other  machines  which  we  have  exam- 
ined. Again,  it  has  the  very  desirable  high  rate  of  alterna- 
tions attained  by  few  others  and  which  can  be  varied  by 
the  motive  power  employed  without  materially  changing 
the  voltage. 

EXPERIMENT  95. — Attach  hand  electrodes  to  the  var- 
ious forms  of  apparatus  in  the  laboratory  for  generating 
the  sinusoidal  current  and  take  the  current  through  the 
body.  Test  the  effect  of  varying  the  speed  at  which  the 
machines  are  run  and  also  of  varying  the  action  of  the 
other  controlling  devices.  Compare  the  sensation  exper- 
ienced with  that  produced  by  the  induction  coil  currents 
and  also  with  that  generated  by  the  magneto  machines. 
Pay  special  attention  to  the  physical  characteristics  of 
the  various  alternating  currents  and  to  their  physiological 
effects. 


THE  INDUCTION  TRANSFORMER  FOR  CAUTERY. 

(T.  224,  228.) 


The  instrument  here  described  (Fig.  43)  is  one  de- 
signed to  change  the  ordinary  alternating  current  used  in 
lighting  circuits  to  a  current  which  is  better  adapted  to  meet 
the  conditions  found  in  a  cautery  circuit.  It  has  been  seen 
that  a  current  in  one  system  is  capable  of 
setting  up  a  current  in  another  system  near 
it  by  induction.  This  is  accomplished  by 
the  rapidly  changing  magnetic  field  of  the 
primary  system  which  extends  to  the  sec- 
ondary system.  A  current  is  thus  set  up 
in  the  secondary  coil  which  exactly  corres- 
ponds in  the  rate  of  alternation  to  that  in 
the  primary.  Except  for  a  certain  loss  in 
the  transformation,  the  electro- motive 
forces  of  the  two  systems  will  be  propor- 
tional to  the  number  of  turns  of  wire  in 
each.  Further,  the  strengths  of  current  in  the  two  sys- 
tems will  be  so  related  that  the  energy  (C  E  =  E)  of  the 
one  will  equal  that  of  the  other.  When  the  secondary  coil 
has  fewer  turns  than  the  primary  the  E.  M.  F.  will  be 
reduced  and  this  is  called  a  "step  down"  transformer. 

The  conditions  required  in  a  current  .for  heating  a 
cautery  are  such  as  demand  a  large  current  at  a  low 
E.  M.  F. ,  and  these  conditions  are  met  when  the  secondary 
coil  is  made  of  few  turns  of  heavy  copper  wire.  The 
strength  of  current  is  nicely  regulated  by  sliding  the  sec- 
ondary over  the  primary  coil.  By  this  method  the  control 
of  the  current  is  so  perfect  as  to  render  a  cautery  rheostat 
in  circuit  entirely  unnecessary. 


Fig.  43. 


HIGH  POTENTIAL,   HIGH    FREQUENCY 
CURRENTS. 


Currents  of  high  tension  and  of  great  frequency  of 
alternations  have  long  been  known  to  the  electro-thera- 
peutist who  is  familiar  with  the  action  of  the  static  machine. 
The  discharge  which  takes  place  between  the  prime  con- 
ductors of  such  a  machine,  when  they  are  supplied  with 
Leyden  jars  or  condensers,  is  at  times  of  this  nature. 
During  the  small  fraction  of  a  second  required  for  such 
discharge,  which  may  be  spoken  of  as  an  instantaneous 
current,  the  electric  polarity  changes  many  thousand  times, 
in  oscillations  of  gradually  diminishing  amplitude.  When 
the  arrangements  during  a  treatment  with  the  static 
machine  in  action  is  such  as  to  make  the  patient  on  the 
insulated  stool  the  terminus  of  the  charge  from  one  of  the 
condensers,  and  a  ball  electrode  connected  to  the  other 
condenser  is  brought  sufficiently  near  the  person  of  the 
patient  to  permit  a  spark  to  pass,  /.  e. ,  the  direct  or  indi- 
rect treatment  by  sparks,  then,  provided  the  relation  of 
capacity  to  resistance  is  just  right,  the  patient  is  subjected 
to  a  current  of  high  frequency  and  high  potential  for  the 
instant  corresponding  to  each  discharge.  Again,  the 
static  machine  may  give  rise  to  high  frequency,  high 
potential  currents  in  what  has  been  termed  the  static  induced 
circuit,  a  current  that  is  obtained  in  a  circuit  connecting 
the  outer  surfaces  or  armatures  of  the  Leyden  jars  or  con- 
densers. The  patient  may  be  made  a  part  of  this  circuit 
and  so  be  subjected  to  the  influence  of  these  high  poten- 
tial, high  frequency  currents. 


106  LABORATORY  MANUAL 

But  as  one  of  the  important  features  of  this  peculiar 
electric  modality  in  its  relation  to  physiological  and  thera- 
peutic action  is  the  oscillatory  character  of  the  discharge, 
the  static  machine  as  it  is  customarily  employed  cannot  be 
depended  upon  with  certainty  to  furnish  a  discharge  of 
this  nature.  Whether  or  not  the  spark  discharge  of  the 
static  machine  is*  impulsive  or  oscillatory  in  character 
depends  upon  the  relation  which  the  capacity  of  the 
machine  and  condensers  bears  to  the  inductance  and 
resistance  of  the  circuit,  and  as  certain  of  these  terms 
vary  from  time  to  time,  due  to  atmospheric  conditions  and 
manner  of  application  the  physical  nature  of  the  discharge 
likewise  varies,  and  therefore  the  static  machine,  in  the 
arrangement  of  its  parts  as  now  employed  in  therapeutics, 
does  not  furnish  the  high  potential  currents  with  such 
invariable  regularity  in  number  and  frequency  of  the 
oscillations  as  is  required  for  accuracy  in  scientific  observa- 
tions and  comparison  of  results. 

If  the  output  of  electric  energy  from  the  static 
machine  was  stabile  and  uniform  the  capacity  of  the  con- 
densers could  be  so  adjusted  to  the  resistance  and  induc- 
tance in  the  circuit  as  to  secure  constancy  in  the  oscillatory 
nature  of  the  discharge  from  them,  but  the  obstacles  to 
this  end  have  not  yet  been  overcome. 

Other  sources  than  the  static  machine  have  therefore 
been  sought  for  and  developed  for  generating  high  poten- 
tial, high  frequency,  currents.  Tesla,  Elihu  Thomson  and 
d'Arsonval  have  each  been  active  in  this  search,  and  each 
in  his  independent  line  of  investigation  has  made  use  of 
large  induction  coils  as  step-up  transformers  of  the  original 
electric  energy,  which  in  some  instances  is  derived  from 
alternating  dynamos  of  low  frequency  and  in  others  from 
some  direct  current  source,  as  a  dynamo,  a  primary  or 


OF    ELECTROTHERAPEUTICS. 


107 


secondary  battery.  The  low  frequency  of  the  alternating 
dynamo  must  be  changed  to  a  high  frequency,  and  the 
constant  or  direct  current  must  be  broken  up  into  sud- 
den impulses  with  interruptions  in  order  to  furnish  the 


T  W  c\  vv  c  V  \  (>  YV  Co  \ 


Fig.  44. 

proper  variations  for  inducing  currents  in  the  windings  of 
the  induction  coil.  These  necessities  give  rise  to  some 
peculiarities  in  mechanism  which  have  been  variously  con- 
structed by  the  different  inventors.  The  underlying  prin- 
ciples by  which  the  ultimate  result  is  secured  are  the  same 


108  LABORATORY  MANUAL 

in  all.      The  accompanying  diagram   (Fig.  44)   will  illus- 
trate the  various  steps  in  the  process. 

B  C  D  is  an  induction  coil  or  transformer  whose  pri- 
mary coil  is  energized  from  some  source,  preferably  an 
alternating  current  dynamo.  If  the- energizing  current  is 
a  direct  current  source  then  the  primary  circuit  would 
need  to  be  supplied  with  an  interrupting  device  to  break 
the  current  into  periods,  such  as  the  spring  vibrator 
attached  to  the  ordinary  induction  coils  or,  what  is  better, 
a  rotating  disk  driven  by  a  motor  and  so  arranged  as  to 
make  and  break  the  circuit  with  great  rapidity  and  sudden- 
ness, as  in  the  method  devised  by  d'Arsonval.  With  the 
primary  coil  excited  in  either  manner  named,  induced 
currents  are  created  in  the  secondary  coil  D,  the  terminals 
of  which  are  joined  to  the  internal  armatures  of  two  con- 
densers or  Leyden  jars  G  G',  between  which  is  arranged  a 
spark  gap  F.  The  external  armatures  of  the  condensers 
H  H'  are  joined  through  a  solenoid  J  of  copper  wire  large 
size  and  about  20  turns.  When  this  system  is  in  action, 
at  each  break  or  alternation  in  the  primary  circuit,  the 
E.  M.  F.  induced  in  the  secondary  coil  charges  the  con- 
densers. In  proportion  to  the  charge  the  difference  of 
potential  between  the  armatures  increases.  When  it 
reaches  the  limit  of  the  area  of  the  ball  terminals  and  the 
space  separating  them  at  the  spark-gap,  which  may  be 
many  thousand  volts,  a  discharge  takes  place  across  the 
air  gap  and  oscillates  between  the  condensers,  while  the 
solenoid  J  is  traversed  by  a  current  of  a  frequency  corres- 
ponding to  the  frequency  of  the  oscillations.  These  oscil- 
lations are  prevented  from  discharging  into  the  circuit  of 
the  secondary  coil  because  of  its  great  self  induction. 
When  operating  the  system  by  energizing  it  from  an 
alternating  dynamo  circuit  the  charging  and  discharging  of 


OF    ELECTROTHERAPEUTICS. 

the  condensers  is  so  frequently  repeated  that  an  arc  is 
likely  to  form  across  the  spark  gap  and  so  put  an  end  to 
the  oscillatory  nature  of  the  discharge.  In  order  to  pre- 
vent the  formation  of  this  arc  Tesla  and  Thomson  em- 
ployed first,  a  strong  magnetic  field  and  later,  an  air  blast 
at  the  spark  gap. 

When  we  compare  the  action  of  this  system  when  ener- 
gized by  the  alternating  dynamo  current,  or  the  interrupted 
direct  current,  we  find  that  with  the  first  the  inductive 
effects  of  the  two  waves  of  positive  and  negative  potential 
are  the  same,  so  that  when  the  alternation  has  a  frequency 
of  124  periods  per  second  as  is  customary  with  the 
ordinary  alternating  dynamo  used  for  industrial  purposes, 
there  will  be  double  the  number  or  248  single  inducing 
waves  each  second.  With  the  direct  current  interrupted  a 
current  effective  in  charging  the  condenser  is  induced  in 
the  secondary  only  at  the  instant  of  "make,"  so  that  to 
have  the  same  number  of  useful  waves  as  with  the  alter- 
nating dynamo  current,  it  would  be  necessary  for  the  in- 
terrupter to  produce  248  contacts  per  second. 

The  currents  that  traverse  the  solenoid  induced  by 
the  discharge  of  the  condensers  to  the  outer  armature  of 
which  the  solenoid  is  connected  are  those  that  are  ordin- 
arily utilized  for  therapeutic  purposes.  By  connecting 
conductors  to  each  end  of  the  solenoid  a  circuit  can  be 
provided  through  which  these  currents  can  be  conveyed. 
This  may  be  termed  the  patient's  circuit,  for  it  is  to  the 
current  generated  at  this  point  that  the  patient  is,  in  one 
or  the  other  manner,  subjected. 

By  an  additional  device,  that  is  another  step-up  trans- 
former, these  currents  may  be  brought  to  generate  others 
of  still  higher  tension.  These  have  been  termed  "  cur- 
rents of  second  order, M  and  are  obtained  by  having  the- 


110  LABORATORY  MANUAL 

solenoid  of  sufficient  diameter  to  permit  of  placing  within 
it  a  glass  tube  enclosing  a  coil  of  fine,  well  insulated  wire, 
of  many  turns  but  a  single  layer.  Currents  of  such  ex- 
tremely high  potential  are  excited  in  this  inner  coil  when 
the  solenoid  is  excited  that  the  glass  -tube  surrounding  the 
coil  of  fine  wire  needs  to  be  filled  with  oil  to  serve  as  an 
insulator.  The  terminals  of  this  fine  wire  coil  brought  out 
at  the  extremities  of  the  glass  tube  through  proper  stop- 
pers can  then  be  connected  up  in  any  manner  desired  so  as 
to  exhibit  the  nature  of  these  "  currents  of  second  order." 
Hertz,  Tesla  and  Thomson  have  each  devised  a  num- 
ber of  beautiful  and  striking  experiments  by  which  to  de- 
monstrate the  energy  possessed  by  these  high  frequency 
and  high  potential  currents.  It  was  early  discovered  that 
they  failed  to  excite  the  animal  organism  either  in  the 
form  of  sensation  or  muscular  movement,  and  yet  after 
traversing  the  body  they  render  lamps  and  vacuum  tubes 
incandescent,  and  in  many  ways  exhibit  an  expenditure  of 
electric  energy  which  if  applied  to  the  animal  body  in 
one  of  many  other  forms  would  prove  instantly  destructive. 

ESSENTIAL     PROPERTIES     OF     HIGH     POTENTIAL     HIGH     FRE- 
QUENCY   CURRENTS. 

As  pointed  out  by  Bordier,  these  currents  are  distin- 
guished from  ordinary  alternating  currents  by  three  essen- 
tial properties,  'which  are  due  to  both  the  great  frequency 
and  the  high  tension. 

ist.     They  cause  remarkable  inductive  effects. 

The  E.  M.  F.  of  induction  near  an  inducing  source  is 
equal  to  the  product  of  the  intensity  of  the  current  by  the 
frequency.  Let  us  suppose  a  frequency  of  500,000  periods 
per  second  and  a  mean  current  of  i  ampere.  The  E.  M. 
F.  in  one  turn  would  be  the  same  as  if  a  current  of  100 


OF    ELECTROTHERAPEUTICS. 


Ill 


amperes  with  a  frequency  of  50  should  circulate  in  10 
turns  of  wire.  Thus  it  is  seen  that  with  high  frequency  the 
E.  M.  F.  induced  in  a  single  turn  would  be  considerable. 
In  a  large  solenoid  the  current  induced  in  one  turn  is  suf- 
ficient to  illuminate  by  mutual  induction  a  lamp  of  8  volts 
and  i  ampere. 

2nd.  Currents  of  high  frequency,  even  though  the 
capacity  be  small,  circulate  as  well  in  open  as  in  closed 
circuits,  so  that  contact  with  only  one  pole  suffices  to  give 
a  current 


Fig.  45. 

In  fact,  feeble  as  may  be  the  capacity,  the  charge  and 
discharge,  repeated  hundreds  of  thousands  of  times  per 
second  at  a  high  potential,  represent  a  notable  mean  cur- 
rent. 

It  is  this  that  explains  the  uni- polar  currents,  and  the 
sparks  that  occur  when  any  point  on  the  solenoid  is 
touched.  In  this  case  the  body,  constitutes  an  insulated 
surface  which,  at  each  oscillation,  is  charged  with  a  very 
nearly  constant  quantity  when  it  is  at  a  certain  .distance 
from  the  solenoid. 

The  corresponding  charge  of  contrary  sign  should  be 


112  LABORATORY  MANUAL 

found  on  the  parts  of  the  solenoid  which  are  at  that 
moment  at  a  different  potential.  This  explains  why  the 
sparks  which  are  drawn  from  the  solenoid  are  greatest  at 
the  extremities  and  least  midway. 

3d.  The  resonant  effects,  which  have  been  so  beau* 
tifully  shown  by  the  experiments  of  Hertz,  and  which  are 
extremely  interesting  to  the  physicist,  but  which  have  not, 
so  far,  been  found  to  have  any  relationship  to  therapeutics. 

METHODS    OF    APPLICATION. 

In  bringing  the  action  of  these  high  frequency  cur- 
rents to  bear  upon  the  human  and  other  animal  organisms 
three  methods  of  application  have  up  to  this  time  been 
employed — suggested  by  the  properties  of  the  current 
which  we  have  enumerated. 

i st.  Auto-conduction.  In  this  mode  of  application 
the  capacity  of  the  current  to  induce  currents  in  objects 
brought  within  their  range,  is  utilized.  In  place  of  the 
small  solenoid  above  described  a  much  larger  one  is  em- 
ployed, composed  of  well  insulated  cable  wire,  and  wound 
about  a  frame  work  capable  of  admitting  into  its  interior 
the  man  or  animals  to  be  treated.  Although  the  person 
enclosed  in  the  solenoid  is  not  in  contact  with  it  at  any 
point,  nevertheless,  while  it  is  in  action,  induced  currents 
of  extreme  energy  and  frequency  of  oscillations  are 
induced  in  his  body.  These  induced  currets  have  their 
seat  in  the  organism  itself  and  act  upon  the  central  nervous 
system  and  deep  seated  organs  and  tissues  as  is  shown  by 
the  effects  produced  and  recorded  in  the  following  article 
on  the  physiological  action  of  these  currents. 

2nd.  The  direct  application.  This  is  made  by  con- 
ducting the  currents  generated  in  the  small  solenoid,  or  the 
currents  of  second  order,  to  any  part  of  the  body  by 


OF    ELECTROTHERAPEUTICS.  113 

means  of  conducting  wires  and  metallic  electrodes  and 
thus  making  the  body  as  a  whole,  or  any  part  of  it,  as  the 
case  may  be,  a  part  of  the  circuit. 

3rd.  Insulation.  In  this  method  the  patient,  person 
or  animal,  to  be  subjected  to  it  is  placed  upon  an  insulated 
platform  and  connected  by  a  wire  to  one  extremity  of  the 
solenoid  while  a  point, -metallic  point  or  plate,  at  some 
little  distance  from  the  insulated  platform  is  connected 
with  the  other  extremity  of  the  solenoid.  The  person 
acted  upon  is  thus,  as  it  were,  made  to  take  the  place  of 
one  of  the  armatures  of  a  condenser  and  is  subjected  to  a 
charge  which  is  slowly  discharged  by  connection  across 
the  interval  between  the  body  and  the  conductor  leading 
to  the  other  extremity  of  the  solenoid. 

PHYSIOLOGICAL    ACTION    OF    HIGH    TENSION,   HIGH    FRE- 
QUENCY   CURRENTS. 

This  form  of  electric  modality,  except  as  it  is  fur- 
nished by  static  or  influence  machines  has  not  so  far  been 
studied  in  its  relation  to  physiological  action  by  many 
persons.  Several  notable  electricians  as  Nikola  Tesla,. 
Elihu  Thomson  and  Hertz  have  done  much  to  acquaint  us 
with  the  apparent  harmlessness  of  this  form  of  electricity 
when  the  living  animal  body,  or  some  part  of  it,  is  made 
the  path  of  its  transit.  But  to  d'Arsonval  and  his  assist- 
ants the  credit  is  mainly  due  for  having  determined  with 
scientific  exactness  and  demonstrated  by  unquestionable 
proofs  that  this  electric  modality  does  in  many  ways- 
modify  physiological  processes  most  profoundly.  While 
we  have  for  a  number  of  months  been  using  this  form  of 
electricity  in  this  laboratory,  as  generated  by  both  the 
Tesla  and  the  Thomson  forms  of  apparatus,  we  have,  so 
far,  done  little  with  it  other  than  to  confirm  many  of  the 


114  LABORATORY  MANUAL 

results  that  d'Arsonval  has  reached  and  which  he  has  pub- 
lished from  time  to  time  in  the  transactions  of  the  Societe" 
de  Biologic  and  of  the  Socie"te"  Internationale  de  Physique. 

What  is  set  forth  here,  therefore,  as  the  result  of 
investigation  as  to  the  relation  of  this  form  of  electricity 
to  physiological  action  in  the  animal  body,  and  which  may 
be  regarded  as  fully  established  by  abundant  experiment, 
is  given  mainly  on  the  authority  of  d'Arsonval,  and  to  the 
detailed  reports  of  his  researches  we  would  refer  any  who 
may  wish  to  examine  into  the  data  upon  which  the  follow- 
ing conclusions  are  based: 

i st.  The  most  singular  and  striking  effect  of  high- 
tension,  high-frequency  currents  is  their  entire  absence  of 
action  on  sensation.  This  is  daily  demonstrated  in  this 
laboratory.  When  the  Tesla  apparatus  is  excited  by  an 
alternating  dynamo  current  and  is  pouring  forth  a  torrent 
of  sparks  between  the  terminals,  across  an  air  gap  of  eight 
or  ten  inches,  one  can  grasp  these  terminals,  one  in  each 
hand,  and  take  the  entire  current  through  the  body  with- 
out experiencing  the  slightest  sensation  except,  perhaps, 
one  of  gentle  warmth  at  the  wrists  when  the  current 
reaches,  or  exceeds  three  amperes.  To  demonstrate  the 
actual  energy  that  is  being  expended  during  this  proced- 
ure it  needs  only  to  have  two  persons  grasp  these  term- 
inals each  with  one  hand  and  then  complete  the  circuit  by 
taking  several  incandescent  lamps  in  series  between  them, 
when  the  lamps,  requiring  each  an  ampere  of  current  and 
TOO  or  more  volts  to  light  them,  will  glow  brilliantly  while 
the  current  is  passing. 

When  the  current  is  caused  to  impinge  upon  a  limited 
surface  of  the  skin  or  mucous  membrane  in  the  manner 
which  in  treatments  by  the  static  machine  is  termed  "the 
breeze  "  the  part  is  soon  benumbed  and  for  a  few  moments 


OF    ELECTROTHERAPEUTICS.  115 

experiences  the  loss  of  sensibility  which  may  go  on  to 
complete  anaesthesia.  This  insensibility  does  not  pene- 
trate deeply  and  lasts  only  a  few  moments,  but  that  it  may 
be  made  to  serve  important  therapeutic  needs  is  at  once 
evident  to  a  physician. 

2d.  These  currents  do  not  excite  muscular  contrac- 
tions. Just  as  the  passage  of  these  currents  through  the 
organism  fails  to  arouse  sensation  so  likewise  motor  nerve 
and  muscle  are  irresponsive  to  them.  While  the  same 
quantity  of  electric  energy  transmitted  under  the  form  of 
alternating  currents  of  long  periods  (100 — 10,000)  and 
much  less  voltage,  would  have  caused  violent  muscular 
contractions,  which  of  themselves  would  suffice  to  kill  the 
recipient,  here  no  contraction  whatever  occurs. 

But  just  as  a  sensory  nerve  when  subjected  to  the 
direct  action  of  these  vibrations  for  a  time  is  rendered 
anaesthetic,  so  a  motor  nerve  may  be  influenced  in  such 
manner  by  these  currents  as  to  be  for  a  brief  period  (10 
to  15  minutes)  incapable  of  responding  to  any  form  of 
excitement. 

3d.  The  high-tension,  high-frequency  currents  im* 
part  an  extraordinary  activity  to  nutritive  changes  and  to 
cellular  life. 

This  has  been  demonstrated. 

(a)  By  examining  and  estimating  in   man   and  ani- 
mals the  products   of  respiratory  combustion  before   and 
after  the  action  of  the   current.     The  oxygen  absorbed  is 
seen  to  be   increased  considerably  and  carbon  dioxide  is 
eliminated  in  greater  quantity. 

(b)  By  the  amount  of  urea  being  greatly  increased 
in  quantity,  as  has  been  determined  by  hundreds   of  uri- 
nary analyses. 

(c)  By   an  increased   heat   production,    which   has 


Il6  LABORATORY  MANUAL 

been  carefully  determined  by  an  ingenious  anemo-calori- 
meter  devised  by  d'Arsonval.  By  this  instrument  it  has 
been  established  that  by  comparing  the  heat  put  forth  by 
the  human  body  before  and  after  this  method  of  electriza- 
tion, it  is  found  to  raise  it  from  79.6  cal.  to  127.4  cal.  per 
hour  at  an  average  temperature  of  17°  C. 

(d)  By  a  loss  of  weight  in  the  men  and  animals 
experimented  on  during  the  period  of  application.  This 
would  of  necessity  be  the  primary  result  of  the  increased 
combustion.  But  it  was  found  that  in  the  intervals  be- 
tween the  applications  of  the  current  there  was  a  rapid 
gain  in  weight. 

4th.  While  there  is  no  perceptible  action  of  these 
currents  on  the  nerves  of  general  sensibility  and  of  volun- 
tary muscle,  the  vaso-motor  nervous  system  which  con- 
trols the  vascular  system  is  influenced  by  these  currents  to 
a  marked  degree.  The  blood  vessels  in  the  ear  of  the 
rabbit  are  seen  to  dilate  rapidly  under  its  action  and  this 
is  followed  a  little  later  by  energetic  contraction.  The 
same  results  take  place  in  man  as  determined  by  the 
sphygmograph  and  sphygmomanometer.  The  blood  pres- 
sure is  at  first  lowered  and  after  a  little  time  rises  and 
remains  elevated. 

5th.  Action  on  unicellular  organisms.  In  order  to 
determine  the  direct  action  of  these  high-frequency,  high- 
tension  currents  on  cellular  physiology  many  forms  of 
bacilli  were  subjected  to  their  influence.  The  cultures  of 
the  pyocyanic  bacillus  were  very  much  attenuated  at  the 
end  of  some  minutes.  The  chromogenous  function  is 
first  suppressed  and  if  the  experiment  is  continued  for 
half  an  hour  the  baccilli  are  killed. 

The  action  of  these  currents  is  found  to  modify  also 
the  products  of  the  secretion  of  bacteria.  The  microbic 


OF    ELECTROTHERAPEUTICS.  Iiy 

toxines  are  found  to  readily  lose  their  virulence  when  sub- 
jected to  this  electric  modality  for  a  short  time. 

D'Arsonval  and  Charrin  have  carried  on  a  series  of 
experiments  for  some  months  to  determine  the  modifying 
action  of  various  forms  of  electricity  on  the  growth  and 
behavior  of  bacteria  the  results  of  which  were  reported  to 
the  French  Academy  of  Sciences,  February  ioth,  1896. 
Their  experiments  have  shown  that  cultures  of  bacteria  are 
affected  more  or  less  by  the  action  of  the  constant  or  gal- 
vanic current,  the  interrupted  induced  current  of  low  ten- 
sion and  frequency,  and  also  by  the  high  tension,  high  fre- 
quency currents.  The  action  of  the  latter  seems  to  be 
most  effective  both  in  retarding  the  growth  of  pathogenic 
bacteria  and  in  weakening  the  virulence  of  their  toxine 
products.  As  has  been  elsewhere  noted,  the  action  of  the 
constant  current  upon  culture  media  is  attended  by  elec- 
trolysis and  is  a  difficult  matter  to  determine,  when  this 
current  is  used,  just  how  much  of  the  result  is  to  be  attri- 
buted to  the  electric  action  directly  and  how  much  to  the 
action  of  the  liberated  ions.  It  is  fair  to  presume  that  the 
changes  wrought  by  the  high  tension,  high  frequency  cur- 
rents are  the  result  of  the  electric  action  solely  since  being 
alternating  currents  but  little  electrolytic  decomposition  at- 
tends them. 

The  experiments  upon  bacterial  toxines  by  means  of 
high  frequency,  high  tension  currents  and  the  subsequent 
tests  made  with  the  solutions  containing  the  toxines  thus 
acted  upon,  not  only  seem  to  show  that  the  toxic  power  is 
reduced,  but  also  that  the  animal  receiving  such  injections 
is  rendered  immune,  or  its  resisting  power  to  such  toxines 
is  greatly  increased.  From  this  the  hope  is  entertained 
that  by  means  of  the  application  of  such  currents  it  may, 
eventually,  be  possible  to  so  attenuate  bacterial  products 


Il8  LABORATORY  MANUAL 

in  the  organism  of  a  patient  as  to   render  him  immune  to 
the  disease. 

6th.  The  clinical  results  are  also  in  evidence  to  prove 
the  modifying  influence  which  electricity  in  this  form  ex- 
erts upon  physiological  action,  and  while  these  are  not  as 
yet  very  abundant  they  are  already  sufficient  in  amount 
and  importance  to  establish  the  value  of  this  unique  man- 
ner of  treatment,  and  are  deserving  of  separate  consider- 
ation in  the  following  article. 

THERAPEUTICS    OF    HIGH    POTENTIAL,    HIGH    FREQUENCY 
CURRENTS. 

Those  who  have  been  long  familiar  with  the  results 
obtained  from  treatments  by  means  of  the  static  machine 
cannot  but  be  struck  with  the  similarity  of  these  with  what 
has  recently  been  set  forth  by  D'Arsonval,  Apostoli  and  a 
few  others  as  the  results  of  their  experience  in  the  thera- 
peutic use  of  high  frequency  currents  obtained  through  the 
variously  devised  forms  of  apparatus  that  they  have  em- 
ployed. Especially  do  the  results  on  general  nutrition  ob- 
tained by  the  spark  and  insulation  methods  of  treatment 
by  the  static  machine  closely  correspond  with  those  re- 
ported as  resulting  from  the  inductive  action  of  the  large 
solenoid.  The  assertion  which  is  often  made  that  "sug- 
gestion "  is  accountable  for  much  that  is  reported  as  re- 
sulting from  this  as  from  other  forms  of  electric  treatment 
falls  to  the  ground  in  the  face  of  the  exact  methods  of  an- 
alysis that  have  been  adopted  in  determining  the  effects  of 
these  currents  on  patients  in  the  public  clinic  and  upon  the 
growth  of  infants  in  the  Maternity  hospital.  But  the  field 
is  open  and  those  who  doubt  may  readily  put  all  assertions 
to  the  proof. 

We   perhaps  cannot  do  better  in  our  attempt  to  set 


OF    ELECTROTHERAPEUTICS.  119 

forth  the  present  state  of  opinion  as  to  the  therapeutic 
range  and  value  of  this  peculiar  electric  modality  than  to 
give  as  succinctly  as  possible  the  conclusions  of  Apostoli, 
whose  clinical  experience  in  this  field  has  been  up  to  the 
present  time  far  more  extensive  than  that  of  any  other 
practitioner. 

They  are  as  follows:— 

ist.  The  alternating  currents  of  high  tension  exercise 
a  powerful  action  on  every  living  organized  body  which  is 
submitted  to  their  influence. 

2nd.  The  best  method  of  treatment  by  means  of 
these  currents  is  to  enclose  the  patient,  without  any  con- 
tact whatever,  in  a  large  solenoid  traversed  by  the  current. 
The  patient  is  thus  completely  insulated  from  the  electric 
source  and  the  currents  which  circulate  by  "auto-conduc- 
tion "  in  his  organism  have  their  origin,  by  induction,  in 
the  tissues  themselves.  The  body  here  plays  the  part  of 
a  closed  circuit. 

3rd.  The  powerful  influence  on  the  vaso-rnotor  sys- 
tem claimed  for  these  currents  by  d'Arsonval  has  been 
verified,  although  the  sensation  immediately  produced  by 
their  passage  is  nil,  and  there  is  no  impression  made  by 
them  on  motor  nerves  or  muscles.  But  an  energetic  ac- 
tion on  all  nutritive  exchanges  may  be  noticed.  This  ac- 
tion shows  itself  by  an  over-activity  of  organic  combus- 
tions and  of  nutrition,  as  has  been  shown  by  the  analysis 
of  the  respiratory  and  urinary  excretions  made  by  d'Arson- 
val,  Berlioz  and  others. 

4th.  The  general  therapeutic  applications  which  fol- 
low from  this  physiological  action  are  confirmed  in  the 
clinic. 

At  the  time  of  this  report  (made  at  the  London  con- 
gress in  '95)  Apostoli  had  in  this  manner  treated  more  than 


120  LABORATORY  MANUAL 

one  hundred  patients,  covering  a  period  of  a  year  and  a 
half,  some  in  his  office  and  some  in  his  public  clinic.  The 
greater  number  of  them  were  much  benefitted  by  this 
method,  which  was  used  to  the  exclusion  of  all  other  treat- 
ment or  medication. 

5th.  These  currents  exercise,  in  the  majority  of 
cases,  a  powerful  and  generally  reparative  action  on  dis- 
eases caused  by  or  attended  with  feeble  nutrition,  by  ac- 
celerating the  organic  changes  and  by  increasing  the  activ- 
ity of  enfeebled  or  perverted  combustion  and  elimination. 
Diuresis  becomes  generally  more  satisfactory  and  excre- 
tion is  hastened. 

6th.  Generally  in  patients  submitted  to  this  influence 
daily  for  about  12  minutes  the  following  effects  are  noticed 
about  in  the  order  named: — 

Return  of  sleep. 

Increase  in  force  and  vital  energy. 

Return  of  good  feeling,  capacity  to  work,  ease  in 
walking,  increase  of  appetite. 

Progressive  and  complete  restoration  of  the  general 
health. 

Often  from  the  first  sittings  and  even  before  the  spe- 
cial and  local  effects  noticed  as  changes  in  the  excretions, 
etc.,  an  amelioration  of  the  general  ill-state  can  be  plainly 
noted. 

7th.  The  local  troubles,  pains  or  trophic  distur- 
bances, subside  generally  much  more  slowly  under  the 
modifying  influence  of  these  currents  than  general  nutri- 
tive disorders.  In  many  cases  such  local  disorders  require 
the  addition  of  local  treatment. 

8th.  Of  all  the  diseases,  which  up  to  the  present  seem 
to  yield  to  this  treatment,  rheumatism  is  most  energetically 
and  effectively  influenced. 


OF    ELECTROTHERAPEUTICS.  121 

9th.  In  some  cases  of  diabetes  the  sugar  has  rapidly 
disappeared  from  the  urine,  while  in  others  it  has  not  been 
perceptibly  diminished  in  spite  of  the  manifest  improve- 
ment in  the  general  state.  This  difference  in  result  may 
foe  due  to  a  lack  of  uniformity  in  technique  or  to  different 
pathological  conditions. 

To  sum  up  in  the  words  of  d'Arsonval,  electricity  in 
the  form  of  high  tension,  high  frequency  currents  is  the 
most  powerful  modifier  of  the  intimate  nutrition  of  the  tis- 
sues that  we  know. 

It  is  a  modifier  which  attacks  life  in  its  most  intimate 
manifestations  and  which  touches  the  working  of  the  liv- 
ing cell  itself.  Its  action  extends  even  to  the  products  of 
the  cell.  As  these  currents  can  with  impunity  traverse  the 
organism  of  living  man  there  is  no  temerity  in  saying  that 
by  means  of  them  an  entirely  new  road  for  therapeutics  is 
opened  up. 

THE  STATIC  MACHINE. 


We  have  in  the  beginning  of  the  preceding  article  dis- 
cussed the  static  machine  as  a  source  of  high  potential 
high  frequency  currents.  While,  as  there  stated,  it  can- 
not be  depended  upon  to  furnish  currents  oscillating  in 
character  or  of  a  uniform  rate  of  oscillations,  yet  the  elec- 
tric modalities  derived  from  the  static  machine  have  for 
many  years  proved  of  valuable  service  in  therapeutics. 

Static,  or  frictional  electricity  is  the  form  in  which 
this  agent  was  first  brought  to  the  intelligent  attention  of 
mankind  and  by  which,  therefore,  it  has  been  longest 
known.  The  physiological  effects  of  the  static  spark  de- 
rived from  the  crude  apparatus  of  Von  Guericke  of  Mag- 
•denburg,  as  early  as  the  middle  of  the  seventeenth  century, 


122  LABORATORY  MANUAL 

was  the  means  of  directing  the  thought  of  physicians  to 
electricity  as  a  therapeutic  resource.  But  the  machinery 
for  generating  static  or  frictional  electricity  had  to  go 
through  many  successive  stages  of  experiment  before  it 
furnished  an  instrument  that  could  be  relied  on  for  thera- 
peutic work. 

The  invention  of  influence  machines  by  Holtz  and  by 
Topler  in  1865  met  this  want,  and  these  with  the  later  in- 
vention of  the  Wimshurst  machine  now  amply  supply  us 
with  instruments  for  dealing  with  such  abnormal  condi- 
tions as  can  be  successfully  combated  by  means  of  static 
electricity. 

In  the  Holtz  machine  the  original  or  primary  charge 
must  be  supplied  to  the  machine,  and  this  under  suitable 
conditions  is  multiplied  by  induction  as  the  movable 
plates  .are  rotated.  When  at  rest,  however,  and  when  the 
atmosphere  is  warm  and  humid,  this  machine  readily  loses 
its  charge  and  is  at  times  recharged  with  much  difficulty. 
The  Topler  and  Wimshurst  machines  are  self  exciting. 
This  feature  in  their  action  is  obtained  through  augment- 
ing the  slight  difference  of  potential  that  usually  exists  by 
means  of  metal  buttons,  more  or  less  in  number,  attached 
at  regular  intervals  to  the  surface  of  the  revolving  plates 
and  projecting  so  as  to  come  in  contact  with  metallic 
brushes  of  tinsel  or  fine  wire  fixed  on  the  ends  of  metal 
rods.  The  friction  caused  by  some  of  these  brushes  aug- 
ments the  initial  charge  while  others  of  them  serve  the 
purpose  of  discharging,  by  contact,  the  electricity  accum- 
ulateoVon  that  part  of  the  plate  which  passes  them.  The 
presence  of  these  brushes,  buttons  and  metal  inductors  on 
the  Topler  and  Wimshurst  machines  are  somewhat  of  a 
detriment  to  their  insulation,  and  in  this  respect  render 
them  inferior  to  the  Holtz,  of  the  same  size,  in  the  amount 


OF    ELECTROTHERAPEUTICS. 


123 


of  electric  energy  produced.  But  the  conditions  which 
furnish  the  initial  charge  by  friction  in  the  former  ma- 
chines are  constant  while  they  are  in  motion,  each  revolu- 
tion adding  its  increment  of  difference  of  potential  from 
this  source,  which  renews  the  supply  of  electricity  and 


FIG.  46.      HOLTZ  MACHINE. 

makes   the   generating   capacity  of   these   machines   more 
constant  and  reliable. 

The  manufacturers  of  the  Holtz  machine  for  medical 
use  have  of  late  years  furnished  it  with  a  small  Wimshurst 
for  the  purpose  of  exciting  action  in  the  Holtz  when  it 
loses  its  charge,  and  the  latest  improved  static  machine  of 
the  Holtz  variety  has  a  small  Wimshurst  included  in  the 
case  with  it,  so  arranged  that  a  charge  from  the  small  ma- 


-124  LABORATORY  MANUAL 

chine  can  be  readily  transferred  to  the  plates  of  the  larger 
one. 

The  Wimshurst  machine  is  especially  reliable  in  crea- 
ting a  difference  of  potential  and  getting  into  action  be- 
cause its  construction  is  such  as  to  give  a  large  amount  of 
friction  between  the  metallic  brushes  on  the  stationary 
plates  and  the  carriers  on  the  revolving  plates.  These 
metal  carriers  or  sectors  are  greater  in  number  than  on 
the  Topler  machine  and  the  arrangement  which  causes  the 
revolving  plates  to  move  in  opposite  directions  favors  a 
rapid  development  of  the  charge.  The  mechanism  of  the 
Wimshurst  is  not,  however,  well  adapted  to  secure  dur- 
ability in  a  machine  of  large  size,  so  that  they  are  not  so 
well  suited  for  developing  quantity  of  electricity  as  either 
the  Holtz  or  Topler  form. 

All  static  machines  for  therapeutic  work  are  now  pro- 
vided with  Leyden  jars  as  condensers,  so  as  to  increase  the. 
quantity  of  electricity  in  the  resulting  spark.  When  the 
machine  is  in  action  the  interior  of  one  Leyden  jar  be- 
comes charged  positively,  the  other  negatively,  and  the 
outer  coating  of  each  jar  by  induction  becomes  charged 
with  an  equal  but  opposite  potential  from  that  within.  By 
leading  off  conductors  from  the  outer  coatings  of  the  Ley- 
den jars,  an  induced  current  can  be  obtained  and  utilized 
for  therapeutic  purposes.  This  current  has  been  named 
by  its  discoverer  the  "static  induced  current"  and  re- 
sembles somewhat  in  nature  the  current  derived  from  the 
fine  wire  coil  of  a  medical  induction  coil,  as  it  is  an  alter- 
nating, and  interrupted  current,  but  its  potential  is  very 
high,  the  E.  M.  F.  being  far  in  excess  of  that  which  any 
medical  induction  coil  can  furnish.  The  frequency  of  in- 
terruptions of  this  current  depends  upon  the  frequency 
-with  which  discharges  take  place  between  the  interior  ar- 


OF  THE 

.UNIVERSITY 


OF    ELECTROTHERAPEUTICS.  125 

matures  of  the  Leyden  jars  at  the  spark  gap  which  sepa- 
rates the  prime  conductors,  and  as  the  width  of  this  spark 
gap  is  under  the  control  of  the  operator  the  number  of  in- 
terruptions and  the  strength  of  the  "static  induced"  cur- 
rent can  be  varied  at  will. 

The  resistance  which  the  static  machine  is  able  to 
overcome  at  the  instant  a  spark  crosses  the  air  gap  be- 
tween the  prime  conductors  shows  us  that  we  are  here 
dealing  with  electricity  in  a  state  of  very  high  potential. 
The  E.  M.  F.  of  the  direct  currents  which  we  have  here- 
tofore considered  as  adequate  for  electro-therapeutic  work 
is  entirely  inadequate  to  carry  a  current  across  the  resist- 
ance of  the  minutest  air  gap.  And  the  most  powerful 
medical  induction  coil  now  in  use  gives  an  E.  M.  F.  cap- 
able of  forcing  a  passage  through  but  an  infinitesimal  film 
of  air  resistance.  But  well  constructed  static  machines  of 
fair  size  will  readily  develop  an  E.  M.  F.  that  will  cause 
the  current  to  leap  an  air  gap  between  the  prime  conduc- 
tors of  eight  or  ten  inches  (20  to  25  cm).  The  E.  M.  F. 
required  to  overcome  the  resistance  offered  by  such  a 
large  interval  of  dry  air  is  enormous.  Although  no  care- 
ful measurements  of  the  E.  M.  F.  of  the  static  machine 
are  yet  recorded,  a  rough  estimate  can  be  made  from  the 
size  of  the  air  gap  traversed  by  the  current  as  shown  by 
the  spark. 

A  spark  i  mm.  in  length  would  indicate  an  E.  M.  F.  of 

at  least.  .  .  .  ...............  .          2,000  volts; 

One  of  i  cm  ............  ...        10,000  volts; 

One  of  10  cm  ..............      100,000  volts; 

One  of  25  cm  ..............    1,000,000  volts 

approximately. 

But  while  the  voltage  is  extremely  high  the  current 
actually  passing  is  exceedingly  small,  seldom  more  than- 
the  fraction  of  a  milliampere. 


126  LABORATORY  MANUAL 

The  spark  is  the  result  of  a  sudden  breaking  down  of 
the  dielectric;  that  is,  the  air  stratum  between  the  prime 
conductors.  "  The  difference  of  potential  has  so  far  in- 
creased by  the  working  of  the  machine  that  the  air  stratum 
no  longer  oilers  sufficient  resistance;  it  is  in  a  state  of 
gradually  increasing  strain  and  finally  gives  way  and  a  dis- 
charge of  electricity  takes  place  equalizing  the  potential. 
The  spark  is  not  itself  electricity,  but  it  is  due  to  the  heat 
and  light  generated  in  the  intervening  particles  of  matter 
as  a  consequence  of  the  mechanical  violence  of  the  dis- 
ruption. The  discharge  which  causes  the  spark  is  ap- 
parently unidirectional  but  in  reality  it  is  oscillatory  in 
character,  the  rapidity  of  the  oscillations  occurring  with 
marvelous  frequency  and  gradually  decreasing  amplitude. " 
The  vibrations  of  one  discharge  may  reach  as  high  as  a 
hundred  million  or  more  per  second. 

The  difference  of  potential  which  is  created  by  the  ac- 
tion of  the  static  machine  seeks  relief  from  the  strain  pro- 
duced on  the  surrounding  insulators  or  dielectrics  in  other 
ways  than  through  the  sudden  disruption  which  causes  the 
spark  discharge.  Foreign  substances  suspended  in  the 
atmosphere  as  dust,  or  water  vapor,  become  charged  with 
electricity  of  different  potentials  and  are  repelled  from  the 
attracted  to  different  parts  of  the  apparatus,  according  to 
the  polarity.  A  stream  of  such  particles  may  produce  an 
actual  current  in  the  air  if  escaping  from  some  point  or 
edge  where  high  degree  of  difference  of  potential  is  main- 
tained. This  is  what  constitutes  the  so-called  "electric 
breeze  "  and  if  it  is  accompanied  by  noise  and  light  it  is 
termed  a  "  brush  discharge." 

It  is  sometimes  desirable  to  know,  when  using  a  static 
machine  in  therapeutic  work,  which  prime  conductor  has 
positive  and  which  negative  potential.  The  position  of 


OF    ELECTROTHERAPEUTICS.  127 

the  prime  conductor  or  Ley  den  jar  will  not  serve  to  desig- 
nate the  potential  since  in  the  action  of  the  machine  the 
potential  may  become  reversed.  The  most  satisfactory 
method  for  determining  which  conductor  is  positive  and 
which  is  negative  is  to  observe  the  machine  while  in  action 
in  the  dark,  when  the  positive  side  can  be  recognized  by 
the  tips  of  the  collecting  comb  showing  points  of  light 
while  upon  the  opposite  or  negative  side  the  light  appears 
in  brush-like  form. 

In  order  that  a  static  machine  may  be  kept  up  to  its 
highest  efficiency  care  must  be  taken  to  preserve  intact  the 
conditions  essential  to  its  action.  Dust  or  moisture  upon 
the  plates  rapidly  equalizes  the  difference  in  potential 
created.  Variations  in  the  amount  of  moisture  in  the  at- 
mosphere affect  the  working  of  the  machine.  It  is  best, 
therefore,  to  have  the  plates  of  the  machine  enclosed  in  a 
case  where  they  can  be  kept  free  from  dust  and  where  if 
necessary  the  air  can  be  subjected  to  artificial  methods  of 
drying,  either  by  means  of  a  dish  containing  petroleum  or 
anhydrous  calcium  chloride  placed  within  the  case.  All 
unnecessary  points  and  projections  should  be  avoided  in 
the  construction  of  the  machine  since  they  serve  to  dissi- 
pate the  electric  energy  produced. 

The  increase  in  the  size  and  number  of  the  plates  in- 
creases the  quantity  of  electricity,  but  there  is  a  point  be- 
yond which  such  increase  possesses  no  additional  thera- 
peutic advantages.  The  prevalent  opinion  at  present 
among  those  experienced  in  the  use  of  static  electricity  in 
therapeutics  is  that  a  machine  having  eight  plates,  four  re- 
volving and  four  stationary,  the  revolving  plates  being 
from  28  to  36  inches  diameter,  is  capable  of  doing  all  that 
is  at  present  sought  for  from  a  machine  of  this  kind. 


128  LABORATORY  MANUAL 

PHYSIOLOGICAL  AND  THERAPEUTIC    ACTION  OF    STATIC  ELEC- 
TRICITY. 

We  have  considered  the  structure  and  action  of  static 
machines  for  therapeutic  work  and  the  physical  properties 
of  the  electric  energy  which  they  produce.  It  remains  for 
us  to  study  the  behavior  of  the  human  organism  in  health 
and  disease  when  subjected  to  electric  conditions  such  as 
the  static  machine  and  its  accessories  can  furnish. 

The  extremely  high  electro-motive  force  of  electricity 
when  generated  by  the  static  machine  renders  it  prone  to 
break  down  the  dielectric  which  surrounds  all  conductors 
and  other  bodies  charged  with  it  and  so  escape.  The  di- 
electrics or  insulators  that  are  employed  in  the  operation 
of  the  static  electric  machines  which  physicians  use  are  the 
glass  plates  of  the  machine  itself,  the  glass  of  the  Leyden 
jars  or  condensers,  the  glass  or  hard  rubber  used  for  the 
various  supports  of  the  conducting  parts  of  the  machine 
as  well  as  for  the  feet  of  the  insulating  stool,  and  lastly, 
the  air  which  surrounds  all  parts  of  the  machine  and  the 
objects  in  continuity  with  its  conductors.  In  order  that 
a  body  may  be  subjected  to  a  high  degree  of  static  charge 
these  various  dielectrics  must  be  capable  of  sustaining  con- 
siderable strain  without  giving  out,  that  is,  there  must  be 
a  sufficiently  thick  layer  of  air  or  glass  or  hard  rubber 
separating  from  surrounding  objects  the  bodies  and  con- 
ductors which  the  machine  has  brought  to  a  positive  po- 
tential so  as  to  prevent  the  charge  from  escaping  to  the 
earth  through  some  object  which  is  in  connection  with  it, 
and  may  serve  as  a  conductor.  Particles  of  moisture  or 
dust  in  the  atmosphere  which  surrounds  the  machine  aid 
in  dissipating  the  charge  which  the  machine  creates,  and 
for  this  reason  a  dry  atmosphere  and  one  free  from  dust 


OF    ELECTROTHERAPEUTICS.  129 

is  an  essential  if  a  static  machine   is  to  do   its  most  suc- 
cessful work. 

The  physical  conditions  created  by  means  of  static 
machines  that  are  employed  in  therapeutics  may  be  enum- 
erated as  follows: 

Static  insulation, 

The  direct  spark, 

The  indirect  spark, 

The  friction  spark, 

The  spray  or  breeze, 

The  needle  spray, 

The  static  induced  current. 

Static  Insulation  or  Charge. — A  patient  to  be  sub- 
jected to  this  condition  sits  upon  the  insulated  stool  or 
platform,  which  is  attached  to  one  or  other,  usually  the 
positive,  pole  of  the  machine  by  means  of  a  conducting 
chain  or  rod.  When  the  machine  is  put  in  motion  the 
body  of  the  patient,  thus  forming  the  terminal  of  the  con- 
ductor, is  raised  to  such  a  potential  as  the  machine  is  cap- 
able of  producing,  and  the  patient  becomes  the  storehouse 
of  a  positive  or  negative  charge,  depending  in  amount 
upon  his  or  her  electrical  capacity.  Just  here  there  is 
need  of  some  careful  study  in  the  comparative  effects  of 
positive  and  negative  insulatioa.  It  is  very  generally 
agreed  among  those  who  have  employed  this  form  of  treat- 
ment that  it  is  followed  by  marked  nutritional  effects,  yet 
some  claim  that  positive  insulation  is  stimulating  and  bene- 
ficial, and  negative  insulation  is  depressing  and  hurtful, 
while  others  assert  that  there  is  no  such  noticeable  differ- 
ence in  effects  between  them,  but  that  either  form  of  in- 
sulation will  prove  tonic  and  invigorating.  Only  a  care- 
fully arranged  series  of  tests  faithfully  carried  out  in  both 
the  domain  of  physiology  and  therapeutics  can  satisfac- 


I3o 


LABORATORY  MANUAL 


torily  settle  this  mooted  question.  It  is  claimed  for  static 
insulation,  and  as  commonly  employed  this  means  positive 
insulation,  that  it  will  elevate  a  subnormal  temperature,  or 
lower  a  temperature  abnormally  high;  that  it  will  regulate 
and  increase  the  volume  of  the  pulse;  that  it  will  decrease 
the  number  but  increase  the  depth  of  respirations;  that  to 
a  person  nervously  excited  and  sensitive,  it  imparts  a  seda- 
tive effect  and  a  sense  of  well  being.  The  action  appears 


Fig.  47. 

to  be  to  improve  nutrition  and  regulate  disordered  func- 
tion, although  the  manner  in  which  a  static  insulation  or 
bath  operates  to  produce  this  effect  has  not  yet  been  ex- 
plained. 

The  Direct  Spark  (Fig.  47). — In  giving  the  direct 
spark,  the  patient  is  placed  upon  the  insulating  platform 
(F),  which  is  connected  by  the  chain  or  rod  to  either  the 
positive  (B)  or  negative  pole  of  the  machine,  and  the  first 
effect  upon  the  patient  (P)  is  to  produce  a  static  charge  of 
either  positive  or  negative  potential,  as  the  case  may  be. 
Here  again  the  positive  charge  for  the  patient  is  ordin- 


OF   ELECTROTHERAPEUTICS.  13! 

arily  used  and  preferred.  An  electrode  (H)  terminating 
in  a  metal  or  gilded  ball  about  two  inches  in  diameter  is 
attached  to  the  other  pole  of  the  machine  (B1).  When 
this  electrode  is  made  to  approach  the  body  of  the  patient 
at  any  point,  the  layer  of  air  which  surrounds  the  patient 
and  acts  as  a  dielectric  is  thereby  rendered  thinner  (G), 
and  less  capable  of  sustaining  the  strain  to  which  it  is  sub- 
jected, and  finally  it  is  so  thinned  by  the  nearer  approach 
of  the  ball  electrode  that  it  gives  way  and  the  static  charge 
in  the  patient's  body  suddenly  becomes  transformed  to 
current  electricity  and  escapes,  leaping  the  air  space  in  its 
transit  and  causing  a  spark. 

The  physical  phenomena  here  are  the  sudden  dissipa- 
tion of  a  static  charge  which  had  been  maintained  in  the 
charged  body  at  a  very  high  potential.  The  discharge  is 
often  if  not  always  oscillatory  in  character,  the  oscillations 
numbering  many  thousands  per  second.  The  current  by 
reason  of  the  extremely  high  resistance  to  be  overcome  at 
several  points  in  the  circuit,  is  very  small,  usually  but  a 
fraction  of  a  milliampere.  The  human  organism,  which  is 
for  us  the  point  in  the  circuit  of  greatest  interest,  is  sud- 
denly subjected  during  a  treatment  of  this  nature  to  a  high 
electric  potential,  which  it  as  suddenly,  loses  as  often  as  the 
ball  electrode  is  brought  sufficiently  near  to  some  part  of 
the  body  to  cause  sparking.  As  all  parts  of  a  charged 
body  are  at  a  uniform  potential  a  change  must  take  place 
throughout  the  entire  organism  when  the  potential  is  re- 
duced to  zero,  as  is  the  case  when  a  spark  crosses  the  air 
gap,  and  if  this  discharge  is  not  instantaneous  in  its  decline 
of  potential  but  oscillatory,  with  gradually  decreasing  am- 
plitude of  oscillations,  the  organism  must  be  subjected  to 
corresponding  disturbances  in  its  molecular  arrangement 
throughout.  The  tissues  of  the  human  body  are  not  uni- 


132  LABORATORY  MANUAL 

form  in  conductive  capacity,  consequently  the  density  of 
the  charge  is  not  uniform  throughout  the  entire  organism. 
Both  during  charge  and  discharge  therefore,  the  human 
body  must  be  supposed  to  act  quite  differently  from  a  mass 
of  metal  of  equal  size  and  form  under  similar  electric  con- 
ditions. Certain  of  the  tissues  conduct  readily  while  others 
possess  the  characters  of  dielectrics.  There  would,  there- 
fore, be  innumerable  spots  of  strain  and  slip  in  close  re- 
lation which  must  be  taken  into  account  when  we  attempt 
to  analyze  the  eifects  produced  during  a  static  treatment. 
But  whatever  may  be  the  fact  as  to  the  spark  discharge 
causing  molecular  excitation  of  the  entire  organism,  a  ser- 
ies of  phenomena  capable  of  ocular  demonstration  always 
occurs  at  that  part  of  the  body  where  the  discharge  takes 
place.  There  is  a  sudden  blanching  of  the  skin,  due  to 
vaso-motor  constriction  over  a  circular  spot  greater  or  less 
in  diameter,  according  to  the  strength  of  the  discharge; 
this  is  soon  followed  by  a  vaso-motor  dilatation  and  the 
spot  is  correspondingly  reddened,  a  condition  which  re- 
mains for  a  considerable  length  of  time  after  the  treat- 
ment. The  muscles  underlying  the  point  from  which  the 
discharge  takes  place  are  caused  to  contract  and  sensa- 
tions of  a  variable  nature,  referred  to  the  same  spot,  are 
prominent  accompaniments.  These  sensations  are  an  im- 
portant element  in  the  treatments  for  upon  their  nature  of- 
ten depends  the  good  or  bad  effect  which  the  patient  ex- 
periences. The  direct  spark  from  small  machines  is  much 
more  likely  to  be  stinging,  pricking  and  irritating  than 
from  large  machines,  and  it  is  claimed  that  grounding  the 
machine  has  the  effect  to  render  the  spark  much  less  dis- 
agreeable than  when  the  circuit  is  confined  to  the  machine, 
the  conductors  and  the  patient,  as  is  the  case  when  using 
the  direct  spark.  The  static  spark  is  of  great  value  in 


OF    ELECTROTHERAPEUTICS.  133 

arousing  to  more  active  nutrition  any  organ  of  the  body 
that  is  subjected  to  this  treatment.  The  skin,  the  vascular 
tissues,  muscles  and  nerves  are  stimulated  by  it.  Its  effects 
are  more  generally  distributed  throughout  the  body  than  is 
the  case  with  the  direct  or  induced  current  applications, 
so  that  it  is  well  suited  for  correction  of  systemic  disorders, 
such  as  rheumatism,  gout,  neurasthenia,  spinal  irritation 
and  general  sluggishness  in  nutrition  from  whatever  cause. 
Unmistakable  evidence  is  given  of  its  power  to  quicken 
nutritive  processes  by  the  way  in  which  the  sweat  and 
sebaceous  glands  are  set  to  work  by  it,  and  the  improved 
bodily  comfort  that  follows  such  applications,  is  due  in  a 
great  measure,  no  doubt,  to  the  more  perfect  elimination 
of  effete  matters  from  the  body. 

It  is  sometimes  difficult  to  give  the  spark  treatment  to 
special  localities  of  the  body  by  means  of  the  ordinary  ball 
electrode  for  the  reason  that  the  current  which  causes  the 
spark  invariably  seeks  the  line  of  least  resistance.  A  di- 
rective electrode,  such  as  the  Morton  electrode  is  of  much 
service  in  getting  exact  local  eifects,  and  by  means  of  it  the 
spark  can  be  drawn  from  accessible  surfaces  within  the 
cavities  of  the  body  when  this  is  thought  desirable. 

The  Indirect  Spark  (Fig.  48.) — In  order  to  get  the 
indirect  spark  the  machine  must  be  "grounded."  This  is 
done  by  putting  the  negative  prime  conductor  or  pole  of 
the  machine  in  communication  with  the  earth  by  means  of 
a  conductor  running  from  it  to  a  convenient  gas  pipe  or 
water-pipe.  The  electrode  used  for  the  purpose  of  draw- 
ing sparks  should  also  be  grounded.  This  has  the  effect 
of  increasing  the  quantity  of  electricity  which  the  machine 
generates  and  improving  the  constancy  of  its  action.  The 
spark  is  likely  to  have  more  volume  and  is  cleaner,  with 
less  irritating  properties.  It  is  more  satisfactory,  there- 


134 


LABORATORY  MANUAL 


fore,  when  using  the  spark  treatment  to  have  the  machine 
grounded.  A  sputtering  series  of  sparks  is  very  disagree- 
able to  most  patients  and  irritates  the  sensory  nerves  and 
should  always  be  avoided  except  when  this  effect  is  sought 
for,  as  in  the  case  when  counter-irritation  or  skin  excita- 
tion is  desired.  It  insures  a  clean,  full,  individual  spark 


I 


Fig.  46. 

to  have  the  machine  well  grounded  and  then  make  the  ball 
electrode  approach  the  part  of  the  charged  body  suddenly 
to  within  the  proper  distance  and  as  suddenly  withdraw  it. 

The  purpose  and  manner  of  the  treatment  with  the  in- 
direct spark  is  the  same  as  that  with  the  direct  spark,  but 
the  effect  differs  because  of  the  physical  and  physiological 
differences  which  they  possess. 

The  Friction  Spark. — This  is  used  mainly  for  ex- 
citation of  the  skin  or  the  superficial  blood  vessels  and  is 
a  convenient  method  for  applying  mild  counter-irritation. 
The  patient  is  insulated  as  with  the  spark  treatment.  A 
roller  electrode  is  provided  for  this  application  but  is  not 
necessary  since  the  large  ball  electrode  will  serve  the  same. 


OF    ELECTROTHERAPEUTICS.  135 

purpose.  The  only  physical  difference  between  this  and 
the  direct  or  indirect  spark  is  that  the  dielectric  is  thinned 
down  to  a  layer  which  is  represented  by  the  thickness  of 
the  patient's  clothing.  The  roller  or  ball  is  passed  over 
the  spot  treated  directly  in  contact  with  the  clothing,  con- 
sequently the  charge  escapes  at  more  frequent  intervals 
and  with  smaller  sparks  but  with  a  prickling,  biting  or 
stinging  effect  upon  the  sensory  nerves  of  the  skin  which  is 
decidedly  exciting  to  their  function  and  the  reflex  effect 
upon  the  nutrition  of  the  skin  is  marked. 

This  form  of  treatment  is  of  special  service  in  correc- 
ting chronic  malnutrition  of  the  skin  as  in  eczema  and  sen- 
sory paresis. 

The  Spray  or  Breeze. — Again  the  patient  is  insu- 
lated as  before  but  the  charge  is  withdrawn,  not  suddenly, 
as  in  the  forms  of  treatment  thus  far  mentioned;  but  slowly 
and  in  infinitesimal  quantity  by  holding  a  pointed  elec- 
trode at  such  distance  from  the  part  of  the  body  to  be 
treated  that  the  discharge  is  not  disruptive  but  is  conveyed 
away  by  the  particles  of  air  forming  the  dielectric  layer, 
each  becoming  charged  with  its  load  and  seeking  the  oppo- 
site potential.  This  creates  a  current  in  the  atmosphere 
surrounding  the  part  of  the  patient's  body  under  treat- 
ment. This  motion  together  with  the  gentle  stimulating 
effect  caused  by  the  slight  loss  of  potential  in  the  surface 
which  each  instant  takes  .place  by  the  process  of  convec- 
tion that  is  going  on,  constitutes  the  treatment. 

The  pointed  electrode  may  be  moved  about  over  the 
patient's  body.  Or,  by  fixing  it  upon  a  stand,  it  can  be  so 
placed  that  the  effect  may  be  maintained  for  any  desired 
length  of  time  upon  a  particular  part.  A  circle  of  points 
fixed  at  a  suitable  distance  above  the  patient  serves  to  dis- 
tribute the  ''spray  "  or <( breeze"  uniformly  over  the  head, 


136  LABORATORY  MANUAL 

The  static  spray  or  breeze  is  peculiarly  soothing  and 
resting  in  its  effects.  By  means  of  it  a  condition  of  ner- 
vous excitement  and  restlessness  can  be  almost  immedia- 
tely allayed.  Severe  headaches  of  a  nervous  type  are  of- 
ten quickly  relieved  and  insomnia  is  frequently  overcome. 

The  Needle  Spray. — When  only  a  part  of  the  pa- 
tient's body  is  brought  in  the  direct  line  of  charge,  and  so 
is  raised  to  a  higher  potential,  as  would  be  the  case  if  the 
conducting  chain  is  held  in  the  patient's  hand  instead  of 
being  placed  on  the  insulating  stool,  and  the  pointed  elec- 
trode is  then  brought  near  enough  to  the  part  to  be  treated 
to  allow  of  minute  disruptive  drops  of  potential  instead  of 
the  discharge  by  convection,  the  effect  upon  the  part  under 
treatment  is  much  as  if  it  was  being  pricked  by  innumer- 
able fine  needles.  This  is  decidedly  stimulating,  though 
at  the  same  time  irritating,  and  is  in  all  respects  of  the 
same  nature  and  used  for  the  same  purpose  as  the  friction 
spark  above  described. 

The  Static  Induced  Current. — The  static  induced 
current  is  that  current  which  results  from  a  return  to  zero 
of  the  difference  of  potential  that  is  created  between  the 
outer  coatings  of  the  Leyden  jars  or  condensers  attached 
to  the  prime  conductors  of  the  machine  (Fig.  49).  At 
each  instant  that  a  discharge  takes  place  between  the  prime 
conductors,  the  potential  difference  which  existed  in  the 
interior  of  the  Leyden  jars  is  equalized  and  a  correspond- 
ing discharge  takes  place  between  the  exterior  surface  of 
these  jars  and  this  latter  current  can  be  utilized  for  thera- 
peutic applications  without  the  disagreeable  accompani- 
ment of  sparks.  The  electrode  for  applying  this  current 
can  also  be  placed  in  contact  with  the  body  and  the  var- 
ious tissues  and  organs  be  brought  under  its  influence  with 
more  precision  than  is  possible  in  the  use  of  the  spark  or 


OF   ELECTROTHERAPEUTICS. 


137 


spray.  All  modern  static  machines  designed  for  therapeu- 
tic work  are  furnished  with  connections  that  permit  the  use 
of  the  static  induced  current.  For  the  regulation  of  this 
current  it  is  only  necessary  to  regulate  the  discharge  be- 
tween the  prime  conductors  of  the  machine.  A  small 
spark  gap  permitting  frequent  minute  discharges  will  be  at- 
tended by  a  similar  frequency  and  feebleness  in  the  static 
induced  impulses.  A  wider  separation  of  the  prime  con- 
ductors will  result  in  heavier  discharges  at  longer  intervals. 
The  strength  and  frequency  of  the  impulses  of  the  static 
induced  current  is  thus  readily  controlled.  The  nature  of 


' 


Fig.  49. 

this  induced  current  is  similar  in  potential  to  that  of  the 
inducing  current.  The  milliamperage  depends  upon  the 
resistance  offered  in  the  circuit.  It  is  in  all  probability, 
at  times  at  least,  oscillatory  in  character,  although  this  re- 
mains to  be  determined  with  certainty.  As  to  the  physio- 
logical effects  and  the  therapeutic  applications  of  the  sta- 
tic induced  current  we  quote  the  words  of  Dr.  Morton, 
whose  rich  experience  in  the  use  of  this  current  gives  to  his 
Conclusion?  the  weight  of  authority. 


138  LABORATORY  MANUAL 

"  Applied  to  a  motor  point,  the  static  induced  current 
produces  most  vivid  and  persistent  muscular  contraction 
with  a  minimum  of  pain;  applied  farther  back  on  the  trunk 
of  a  motor  nerve  it  throws  large  groups  of  muscles  into 
contraction.  The  contraction  is  peculiarly  painless  as 
compared  with  that  of  faradic  coils,  and  the  influence  is 
remarkably  effusive.  Accompanying  a  contraction  of  a 
large  group  of  muscles  is  a  peculiar  sensation  of  lightness 
and  buoyancy  of  the  member.  The  painlessness,  diffusive- 
ness, and  buoyancy  may  all  be  experienced  by  holding  the 
two  electrodes  in  the  hands,  and  taking  a  current  as  strong 
as  possible.  Most  people  will  readily  submit  to  flexions 
successively  at  the  wrists,  elbows,  and  even  to  the  shoul- 
ders before  insisting  upon  taking  no  more.  The  arms  dur- 
ing the  passage  of  the  current  feel  as  if  made  of  cork,  and 
this  feeling  of  lightness  persists  for  some  time.  It  is  the 
same  feeling,  doubtless,  though  here  exaggerated,  as  is 
commonly  referred  to  as  the  refreshing  effect  of  general 
electrization.  The  quality  of  the  current  is  such,  that  while 
energetically  exciting  the  motor  function  of  the  nerve  fila- 
ments, it  fails  to  excite  or  may  even  annul,  to  an  extent, 
the  sensation  of  muscular  pain.  Its  penetrating,  diffusive, 
painless  effect,  with  strong  muscular  contractions,  adapt 
it  admirably  to  general  application  over  the  entire  body  as 
an  electric  in  place  of  an  ordinary  massage. 

"  It  is,  of  course,  applicable  to  every  form  of  muscu- 
cular  paralysis,  for  there  is  no  practical  stimulus  to  nerve 
and  muscle  except  the  electric,  and  none  more  energetic 
than  this  form  of  it 

"  Its  effects  upon  the  Hallerian  irritability  of  the  mus- 
cular tissue  necessarily  includes  an  effect  upon  the  local 
circulation  of  a  part  and  upon  the  lymphatics,  and  to  this 
may  doubtless  be  referred  many  clinical  results  of  relief 


OF     ELECTROTHERAPEUTICS.  139 

as  in  lumbago  and  all  forms  of  muscular  rheumatism,  sub- 
acute  and  chronic  rheumatic  affections  of  the  joints,  ovar- 
ian or  pelvic  pain,  sciatica  or  other  neuralgias. 

"The  second  prominent  characteristic  of  this  current 
is  its  power  of  relieving  pain.  Leaving  out  of  sight  the 
part,  be  it  more  or  less,  played  by  circulatory  changes  re- 
ferred to,  in  this  respect  there  seems  to  exist  a  specific 
analgesic  quality  in  the  current.  The  cotton  feeling  in 
the  hands  and  subjective  sense  of  buoyancy  in  the  arms  is 
in  itself  an  evidence  of  this.  But  the  effect  upon  pelvic 
pain,  upon  ovaritis,  upon  neuralgias,  pleuritic  'stitches,' 
tonsillitis,  and  many  other  pain  affections  is  still  better 
evidence.  In  sciatica,  for  instance,  the  sensation  of  pain 
is  frequently  quickly  relieved  and  a  cure  obtained,  though 
I  think  in  this  case  the  cause  is  two-fold — that  is  to  say, 
due  to  both  the  circulatory  and  the  analgesic  effect.  The 
same  I  believe  to  be  true  in  the  pelvic  and  ovarian  pains. 

"  The  results  in  such  cases,  in  my  opinion,  are  far 
superior  to  anything  obtainable  by  a  faradic  or  a  galvanic 
application.  An  ordinary  faradic  current  will  increase  the 
pain;  the  galvanic  will  very  often  relieve  it.  But  we  have 
in  the  static  induced  current  no  comparison  to  the  electro- 
tonic  and  polar  effects,  or  in  general  the  electrolytic  effects 
of  the  direct  or  galvanic  current.  Therefore,  when  the 
static  induced  current  has  failed  to  act  favorably,  we  should 
try  the  galvanic,  and  vice  versa.  As  no  observations  on 
the  purely  analgesic  effects  of  this  current  have  hitherto 
been  made,  I  must  leave  others  to  test  the  question  for 
themselves." 

It  will  be  seen  from  this  brief  review  of  the  methods 
of  practical  application  of  the  effects  obtained  by  means 
of  the  static  machine  that  it  is  capable  of  doing  a  variety 
of  work  in  therapeutics  which  no  other  form  of  electrical 


140  LABORATORY  MANUAL 

apparatus  can  accomplish;  but  the  good  results  obtainable 
can  only  follow  when  the  action  of  the  machine  is  fully 
understood  by  the  operator  and  the  case  to  be  treated  is 
one  adapted  to  the  form  of  treatment  employed. 

EXPERIMENT  96. — Turn  the  crank  of  the  static  ma- 
chine until  the  sparks  are  passing  between  the  prime  con- 
ductors. Notice  the  difference  in  this  discharge  when  the 
Leyden  jars  are  attached  and  when  they  are  not.  Also 
notice  the  effect  of  connecting  and  disconnecting  the 
metal  coatings  on  the  outer  surface  of  the  Leyden  jars. 
What  is  the  explanation  of  these  differences? 

EXPERIMENT  97. — Determine  which  prime  conductor 
is  charged  positively  and  which  negatively.  Observe 
what  effect,  if  any,  the  discharge  has  upon  litmus  paper. 
Does  it  electrolize?  Does  it  move  the  needle  of  the 
galvanometer? 

EXPERIMENT  98. — Positive  Insulation. — Let  some 
member  of  the  class  take  the  place  of  a  patient  and  sit 
upon  a  stool  placed  upon  the  insulated  platform.  Connect 
the  subject,  by  means  of  a  well-insulated  conducting  cord, 
with  that  prime  conductor  of  the  static  machine  which  is 
charged  positively  when  the  machine  is  in  action. 

Separate  the  prime  conductors  of  the  machine  so  that 
no  discharge  takes  place  across  the  space  between  them. 
After  the  machine  has  been  in  action  for  a  few  moments 
notice  that  an  electric  discharge  will  readily  take  place  at 
any  point  on  the  subject's  body  which  is  approached  by  a 
conductor,  as,  for  instance,  the  finger  of  the  operator. 
This  shows  that  the  subject's  body  has  received  a  static 
charge  of  positive  potential. 

EXPERIMENT  99.  —  Direct  Spark.  —  Separate  the 
prime  conductors  and  unite  by  a  conducting  cord  the  outer 
surfaces  of  the  Leyden  jars.  Connect  the  subject  on  the 


OF    ELECTROTHERAPEUTICS.  i^l 

the  insulated  platform  with  the  prime  conductor  charged 
positively. 

Let  someone  take  the  place  of  operator  and  connect 
a  large  ball  electrode  to  the  negatively  charged  prime 
conductor  by  means  of  a  suitable  cord.  Then  holding 
the  ball  electrode  by  the  insulating  handle  and  putting  the 
machine  in  action  let  him  bring  the  ball  electrode  near  to 
some  part  of  the  subject's  body,  such  as  the  shoulder  or 
back,  until  a  spark  discharge  takes  place. 

EXPERIMENT  100.  —  Indirect  Spark.  —  With  the 
prime  conductors  separated  and  the  outer  surfaces  of  the 
Leyden  jars  connected  have  the  subject  connected  with 
the  positively  charged  prime  conductor,  as  in  the  pre- 
ceding experiment.  Join  the  negatively  charged  prime 
conductor  with  some  near  at  hand  gas-pipe  or  water-pipe 
which  has  a  ground  connection.  This  "grounds"  the 
machine.  To  the  same  or  another  water  or  gas-pipe  the 
ball  electrode  is  then  connected  and  brought  near  to  some 
part  of  the  subject's  body  as  before  until  a  spark  discharge 
takes  place. 

EXPERIMENT  101. — Friction  Spark. — Let  the  ar- 
rangement for  the  subject  and  the  connections  be  the  same 
as  in  giving  the  direct  or  indirect  spark.  The  operator 
should  then  place  the  ball  electrode  upon  some  not  very 
sensitive  part  of  the  subject's  body,  such  as  the  back  or 
limbs,  and  as  closely  in  contact  with  the  skin  as  the  cloth- 
ing will  permit.  Then  with  the  machine  in  action  the  ball 
electrode  should  be  moved  about  over  the  parts  of  the 
body  to  be  treated  and  kept  in  contact  with  the  clothing. 
The  charge  is  discharged  by  means  of  fine  and  frequent 
sparks  giving  a  decidedly  counter  irritant  effect. 

EXPERIMENT  102. — The  Static  Breeze. — With  sub- 
ject and  connections,  as  in  the  preceding  experiment,  sub- 


142  LABORATORY  MANUAL 

stitute  for  the  ball  electrode  a  metal  circlet  with  points 
and  suspend  it  a  few  inches  above  the  subject's  head. 

Or,  instead  of  a  ball  electrode,  let  the  operator  use 
one  terminating  in  a  sharp  point  and  move  it  about  near 
the  part  of  the  body  of  the  subject  that  is  to  be  treated. 
How  does  this  method  of  discharge  differ  physically  from 
that  which  causes  a  spark? 

EXPERIMENT  103. — Static  Induced  Current.— To 
the  outer  metal  coatings  of  the  Leyden  jars  connect 
electrodes  such  as  are  used  to  give  a  treatment  with  the 
induction  coil  current.  Separate  the  prime  conductors  so 
as  to  leave,  at  first,  not  more  than  a  quarter  inch  gap  be- 
tween them.  With  the  subject  on  the  insulated  stool  place 
the  electrodes  on  the  part  of  the  body  that  you  wish  to 
treat  and  set  the  machine  in  motion.  Observe  that  the 
strength  of  this  current  is  determined  by  the  length  of  the 
spark  gap  which  you  maintain  between  the  prime  con- 
ductors, which  can  be  varied  at  will. 


DIAGNOSIS  BY  RONTGEN,   OR  X-RAYS. 

Any  advance  or  improvements  in  methods  of  diag- 
nosis is  a  substantial  gain.  Electricity  had  already  done 
much  to  render  the  diagnosis  of  disorders  of  the  muscular 
and  nervous  system  and  pelvic  organs  more  exact,  but  re- 
cent discoveries  of  the  effect  of  the  action  of  high  tension 
currents  of  electricity  in  vacuum  tubes  have  greatly 
enlarged  its  field  of  usefulness  in  diagnosis  and  both  sur- 
geon and  physician  are  now  able  to  add  the  sense  of 
sight  to  that  of  touch  and  hearing,  in  determining  the 
state  and  condition  of  the  deep  seated  tissues  of  the  body. 

No  one  can  as  yet  set  any  limit  to  the  practical  appli- 


OF    ELECTROTHERAPEUTICS.  143 

cations  that  will  be  made  of  Rftntgen  rays  in  revealing  what 
to  human  vision  is  otherwise  unseen.  Already  the  mem- 
bers of  the  medical  profession  have  found  from  them  such 
help  as  to  give  promise  that  the  date  of  Rontgen's  discov- 
ery will  mark  a  period  of  advance  in  medical  science  as 
important  as  the  discoveries  of  Jenner  or  of  Lister. 
Already  enough  has  been  done  to  show  that  not  only  all 
parts  of  the  bony  skeleton,  with  its  defects  can  be  por- 
trayed in  minute  and  exact  detail,  but  the  structure  of  the 
softer  tissues  and  organs,  also,  their  normal  outlines  and 
density,  together  with  their  departure  from  the  normal 
have  to  some  extent  been  revealed  to  sight. 

So  far  as  is  at  present  known  the  creation  of  these 
peculiar  rays  by  means  of  which  the  human  eye  is  enabled 
to  see,  pictured  upon  fluorescent  screen  or  photographic 
plate,  the  things  of  the  body  hidden  beneath  the  surface, 
is  dependent  upon  the  action  of  the  electric  current.  This 
gives  rise  to  another  demand  upon  the  medical  profession 
to  become  practically  familiar  with  the  phenomena  of 
electric  physics.  The  essentials  for  skiagraphic  diagnosis 
are: — 

Some  kind  of  apparatus  for  generating  a  suitable  elec- 
tric current. 

A  Crookes  tube. 

A  fluorescent  screen  or  photographic  plate. 

CURRENT  GENERATORS  FOR  RONTGEN  RAYS. 

There  are  three  forms  of  electric  apparatus  which 
have  so  far  been  used  to  generate  currents  suitable  for  pro- 
ducing X-rays; 

The  ordinary  induction  coil; 

The  static  or  influence  machine,  and 

The  disruptive  discharge  coil. 


144  LABORATORY  MANUAL 

By  the  ordinary  induction  coil  we  mean  one  of  the 
ordinary  form  of  construction,  such  as  the  Ruhmkorif  coil 
pattern,  with  a  vibrating,  or  what  is  better,  a  rotating  com- 
mutator break.  This  form  of  electric  generator  has  been 
used  more  than  any  other  by  those  who  have  experimented 
with  X-rays.  The  interest  in  this  subject  has  stimulated 
manufacturers  to  produce  excellent  instruments  of  this  kind 
until  now  very  reliable  Ruhmkorff  coils,  capable  of  giving 
a  six,  eight  or  ten-inch  spark  between  the  secondary  termi- 
nals can  be  obtained. 

It  may  be  safely  said  that  a  high  potential  capacity  in 
the  electric  generator  is  the  first  essential  to  successful 
X-ray  work.  So  that  if  a  Ruhmkorff  coil  is  used  its  ca- 
pacity should  be  considerable.  One  giving  a  three  or  four- 
inch  spark  will  serve  for  generating  rays  capable  of  mak- 
ing shadow  pictures  of  the  extremity  of  the  body,  but 
stronger  action  is  required  if  the  thorax,  abdomen  or 
pelvis  needs  to  be  traversed  by  the  rays.  It  is  best  to  take 
the  initial  current  used  to  excite  the  coil  from  some  con- 
stant and  uniform  source  of  supply  as  storage  batteries  or 
a  direct  current  dynamo  circuit  such  as  is  used  in  some 
places  for  producing  incandescent  light.  The  intensity 
of  current  needed  depends  very  much  upon  the  condition 
of  the  tube  that  is  used,  but  with  a  coil  of  large  capacity 
the  action  of  the  coil  can  be  varied  to  suit  the  require- 
ment of  the  tube. 

A  Static  Machine,  when  run  by  a  motor,  and  con- 
stant in  action  is  a  good  Rontgen  ray  exciter  because  of 
the  high  potential  it  creates.  It  is  the  current  resulting 
from  induction  in  the  outer  coating  of  the  Leyden  jars 
attached  to  the  prime  conductors  of  the  static  machine 
that  is  used — the  so-called  "static  induced"  current. 
Rather  more  care  is  needed  to  preserve  the  tubes  from 


OF    ELECTROTHERAPEUTICS.  145 

perforation  when  using  the  static  machine  as  a  generator 
than  when  using  the  coil  since  there  is  liable  to  be  consid- 
erable variation  in  the  strength  and  volume  of  the  sparks 
between  the  prime  conductors  even  with  the  same  spark- 
gap  interval.  A  four  or  six  plate  machine  with  plates  of 
from  twenty- four  to  thirty-six  inches  in  diameter,  if  its  ac- 
tion is  good,  will  serve  very  well  as  an  X-ray  producer. 

But  if  we  are  to  depend  upon  ROritgen  rays  and  skia- 
graphs or  flouroscopes  to  aid  us  in  diagnosis  there  must  be 
no  limit  to  the  quantity  or  penetrating  power  of  the  needed 
rays.  Both  the  Ruhmkorff  coil  and  the  static  machine 
have  their  limitations.  In  the  former  they  are  due  to  its 
mechanical  construction  and  in  the  latter  the  expense 
and  lack  of  constancy  in  action.  Some  form  of  cheaply 
constructed  disruptive  discharge  coil  of  the  Tesla  or 
Thomson  type  producing  high-tension,  high-frequency 
currents,  and  which  could  be  attached  to  a  dynamo  circuit,, 
such  as  is  now  so  universally  employed  for  illuminating 
purposes,  gives  promise  of  meeting  the  requirements  in 
furnishing  a  convenient  and  reliable  source  of  electric, 
energy  of  any  potential  desired  for  exciting  vacuum  tubes. 

Under  these  conditions  torrents  of  high  fre- 
quency discharges  pass  between  the  discharging  knobs, 
of  the  induction  coil  which  are  separated  to  the  dis- 
tance of,  perhaps,  5  millimeters,  the  frequency  being 
determined  by  the  capacity  and  inductance  of  the  Leyden 
jar  circuit  including  the  Tesla  primary.  These  high-fre- 
quency discharges  induce  in  their  turn  high-frequency  and 
high-potential  discharges  in  the  tube.  In  such  cases  both 
electrodes  of  the  tube  are  alternately  cathodes,  and  the 
glass  wall  opposite  to  each  electrode  becomes  fluorescent 
and  therefore  the  source  of  Rontgen  rays. 


10 


146  LABORATORY  MANUAL 

VACUUM    TUBES. 

Perhaps  no  part  of  the  apparatus  required,  in  the 
present  stage  of  our  knowledge,  for  the  production  of 
Rontgen  rays  has  received  so  much  attention  as  the  vacuum 
tubes  in  which  the  antecedent  cathode  rays  are  generated. 
A  volume  could  be  written  upon  this  subject  and  what 
can  be  said  in  a  few  paragraphs  will  perhaps  to  some 
appear  very  meagre.  We  must  refer  those  who  wish  to 
investigate  the  subject  more  deeply  to  the  pages  of  the 
electrical  and  scientific  journals  or  to  some  special  work 
on  the  subject. 

Success  in  making  skiagraphs  depends  very  largely  on 
a  familiarity  on  the  part  of  the  operator  with  the  action  of 
the  tube  and  the  changes  that  may  take  place  in  it  while 
undergoing  bombardment. 

Shape  of  the  Tube. — It  is  now  well  known  that  the 
best  tubes  for  producing  efficient  X-rays  are  those  so  con- 
structed as  to  concentrate  or  focus  the  cathode  rays  either 
on  a  reflecting  surface  within  the  tube  or  a  convenient 
spot  on  the  wall  of  the  tube  itself. 

The  source  of  the  X-rays  is  the  point  against  which 
the  cathode  rays  are  first  projected.  Whether  this  be  the 
wall  of  the  tube  or  some  other  surface  within  the  tube. 
The  cathode  rays  can  be  concentrated  upon  this  point 
both  by  the  shape  of  the  cathode  electrode  and  the  shape 
of  the  vacuum.  It  is  well,  therefore,  to  give  such  con- 
vexity to  the  shape  of  the  cathode  as  will  focus  the  cath- 
ode rays  at  a  desired  point.  Cathode  terminals  made  of 
aluminum  seem  to  work  best,  and  since  the  material  of 
the  cathode  is  gradually  worn  away  by  the  action,  the  size 
and  thickness  should  be  considerable.  If  it  is  designed 
to  have  the  cathode  rays  first  strike  the  wall  of  the  tube 
and  there  create  X-rays,  the  anode  terminal  may  be  of 


OF    ELECTROTHERAPEUTICS.  147 

aluminum  also  and  terminate  in  a  point  or  in  a  ring;  the 
latter  is  better  since  it  does  not  heat  so  quickly.  But  if 
the  anode  terminal  is  to  be  used  as  the  point  of  contact  or 
impingement  of  the  cathode  rays  and  so  generate  the 
X-rays,  then  it  is  best  to  have  it  made  of  a  sheet  of  plat- 
inum and  set  at  such  angle  as  will  direct  the  X-rays  to 
emerge  at  the  spot  on  the  tube  where  the  glass  has  been 
purposely  blown  thin.  When  the  X-rays  are  once  created 
their  escape  from  the  tube  should  be  facilitated  as  much 
as  possible,  and  this  is  best  done  by  having  the  glass  at 
the  point  of  their  exit  blown  as  thin  as  is  consistent  with 
the  safety  of  the  tube. 

A  long  narrow  tube,  therefore,  with  comparatively 
thick  walls,  but  thinned  opposite  the  point  of  impact  or 
emergence  of  the  X-rays  appears  to  be  the  most  efficient 
shape.  The  best  work  has  been  obtained  from  this,  or 
from  some  form  of  " focus"  tube.  The  length  of  the 
tube  should  be  selected  to  correspond  with  the  potential 
used.  The  higher  the  potential  the  longer  the  tube  will 
need  to  be,  and  if  a  very  high  potential,  as  from  a  disrup- 
tive discharge  coil,  is  used,  it  may  be  found  necessary  to 
limit  the  electro-static  action  created  about  the  tube  by 
immersing  it  in  oil. 

The  Vacuum. — More  seems  to  depend  upon  the  elec- 
tric potential  employed  than  the  degree  of  rarefaction 
within  the  tube,  for  even  with  comparatively  low  vacua 
X-rays  are  generated  with  high  potentials.  The  vacuum 
increases  very  much  during  the  action  of  the  tube.  This 
is  thought  by  some  due  to  an  actual  propulsion  of  mole- 
cules through  the  walls  of  the  tube,  while  others  believe 
the  walls  absorb  and  retain  the  gaseous  particles.  When 
from  action  the  vacuum  grows  so  high  as  to  impede  the 
discharge  through  the  tube,  it  can  be  readily  reduced  by 


I48  LABORATORY  MANUAL 

gently  heating  the  tube  with  the  flame  of  a  spirit  lamp  or 
Bunsen  burner.  The  heating  appears  to  set  free  the  gas- 
eous particles  from  the  walls  of  the  tube.  The  degree  of 
vacuum  suitable  for  generating  X-rays  bears  direct  rela- 
tionship to  the  electric  excitation  and  the  best  action  of 
any  tube  can  only  be  determined  by  experience  with  it. 

Action  in  the  Vacuum  Tube. — This  has  been  most 
graphically  and  accurately  portrayed  by  Tesla.  "When 
the  Crookes  phenomena  show  themselves  most  promi- 
nently there  is  a  reddish  streamer  issuing  from  the  elec- 
trode, which  in  the  beginning  covers  the  latter  almost 
entirely.  Up  to  this  point  the  bulb  practically  does  not 
affect  the  sensitive  plate  although  the  glass  is  very  hot  at 
the  point  of  impact.  Gradually  the  reddish  streamer  dis- 
appears, and  just  before  it  ceases  to  be  visible  the  bulb 
begins  to  show  better  action,  but  still  the  effect  upon  the 
plate  (or  screen),  is  very  weak.  Presently  a  white  or 
even  bluish  stream  is  observed,  and  after  some  time  the 
glass  on  the  bottom  of  the  bulb  gets  a  glossy  appearance. 
The  heat  is  still  more  intense  and  the  phosphorescence 
through  the  entire  bulb  is  extremely  brilliant.  One  should 
think  that  such  a  bulb  must  be  effective,  but  appearances 
are  often  deceitful,  and  the  beautiful  bulb  still  does  not 
work.  Even  when  the  white  or  bluish  stream  ceases  and 
the  glass  on  the  bottom  is  so  hot  as  to  be  nearly  melting, 
the  effect  on  the  plate  is  very  weak.  But  at  this  stage 
there  appears  suddenly  at  the  bottom  of  the  tube  a  star- 
shaped  changing  design,  as  if  the  electrode  would  throw 
off  drops  of  liquid.  From  this  moment  on  the  power  of 
the  bulb  is  increased  ten-fold,  and  at  this  stage  it  must 
always.be  kept  to  give  the  best  results." 


OF  ELECTROTHERAPEUTICS.  149 

FLUORESCENT  SCREENS  AND  SENSITIZED  PLATES. 

The  quality  which  certain  substances  possess  of  fluor- 
escing  when  exposed  to  these  invisible  rays  was  not  only 
the  road  to  their  discovery,  but  serves  as  a  very  ready 
means  for  detecting  the  presence  and  quantity  of  the  rays. 
Rontgen  made  use  of  a  fluorescing  screen  made  of  platino- 
cyanide  of  barium.  Salvioni  had  none  of  this  material  at 
hand  when  he  wished  to  construct  what  he  has  termed  his 
cryptoscope,  but  tried  calcium  sulphide,  which  he  found 
worked  very  well.  He  spread  it  on  to  the  card-board  end 
of  a  tube  by  means  of  fish-glue,  while  in  the  end  of  the 
tube  near  the  eye  he  placed  a  lense  which  made  the  card- 
board phosphorescing  under  the  influence  of  the  X-rays, 
more  distinctly  visible.  Following  in  this  line  of  experi- 
ment Edison  not  only  discovered  a  long  series  of  substances 
which  fluoresce  under  the  influence  of  X-rays,  but  he  found 
among  them  tungstate  of  calcium  to  be  by  far  the  most 
efficient,  and  from  these  researches  fluoroscopes  were  de- 
veloped which  now  are  indispensable  to  skiagraphy.  A 
thin  flim  of  fluorescing  material  placed  in  contact  with  the 
photographic  plate  greatly  reduces  the  time  of  exposure  for 
making  a  negative. 

The  fluoroscope  does  not  take  the  place  of  the  sensi- 
tized plate  in  diagnosis,  for  the  shadows  cast  upon  it  are 
not  so  sharp  and  distinct  as  those  formed  on  the  photo- 
graphic film,  and  it  leaves  no  permanent  record.  Yet  it 
serves  as  a  rough  and  ready  means  for  examination  and  is 
most  helpful  in  determining  the  action  of  the  tube  and  fix- 
ing upon  the  best  time  for  an  exposure  of  the  plate. 

Serious  injury  to  the  skin  and  sometimes  to  deeper 
tissues  is  caused  by  too  prolonged  or  too  intense  action 
upon  them  of  some  influence  emanating  from  the  excited 
Crookes  tube.  While  it  is  not  yet  positively  known  what 


150  LABORATORY  MANUAL 

causes  this  injury,  it  is  in  all  probability  due  to  a  bombard- 
ment of  the  tissues  by  microscopic  particles  of  metal  or 
glass  carried  off  from  the  metal  of  the  electrodes  or  the 
glass  of  the  tube  and  driven  into  the  tissues  by  the  action 
of  the  static  charge  which  they  possess.  It  is  found  that 
if  a  thin  sheet  of  aluminum  or  wire  gauze  of  the  same 
metal  is  placed  between  the  Crookes  tube  and  the  part  of 
the  body  being  skiagraphed,  and  is  then  grounded  it  will 
effectually  prevent  any  injury  to  the  tissues.  As  such  a 
grounded  screen  would  serve  to  draw  the  static  charge  as 
well  as  to  intercept  the  particles,  the  result  of  its  action 
well  accords  with  the  theory  above  advanced  as  to  the  cause 
of  such  injury. 

EXPERIMENT  104. — Excite  the  Crookes  tube  by  means 
of  the  static  machine  or  the  induction  coil,  and  observe  by 
means  of  the  fluoroscope  the  relation  between  the  naked- 
eye  appearance  of  the  tube  and  the  illumination  of  the 
fluoroscope  screen.  Observe  the  denning  power  of  the  rays 
on  the  bones  and  joints  of  your  hand  and  wrist,  placing 
the  hand  undergoing  examination  directly  in  contact  with 
the  outer  surface  of  the  fluoroscope. 

EXPERIMENT  105. — Use  a  six  by  eight  sensitized  plate 
or  film  enclosed  in  a  thick  layer  of  dark  paper  or  in  a  plate- 
holder,  and  placing  some  part  of  your  hand  or  arm  in  con- 
tact with  it  at  a  distance  of  eight  or  ten  inches  from  the 
Crookes  tube,  excite  the  tube  for  four  or  five  minutes  in 
such  manner  as  you  have  found  generates  X-rays  most 
abundantly.  Then  carefully  develop  the  plate  or  film  and 
study  the  result.  Be  careful  not  to  expose  the  sensitized 
plate  to  the  action  of  the  X-rays  before  you  are  ready  to 
make  the  picture  or  after  it  is  taken. 


RELATION    OF     MAGNETISM     TO    LIVING    OR- 
GANISM. 


The  intimate  relationship  existing  between  electricity 
and  magnetism,  the  inseparableness  of  their  phenomena, 
make  it  more  than  probable  that  when  electric  energy  is 
operating  magnetic  stress  must  be  credited  with  a  portion 
of  the  work  accomplished,  and  vice  versa.  Whenever  a 
current  of  electricity  traverses  an  animal  body  in  any 
direction  the  magnetic  field  resulting  from  the  passage  of 
the  current  and  surrounding  its  path  must  disturb  in  some 
manner  the  molecular  and  atomic  activities  that  are  going 
on  within  its  range  in  the  tissues  and  fluids  through  which 
the  current  of  electricity  passes.  The  amount  of  this  dis- 
turbance will  depend  upon  the  strength  and  character  of 
the  magnetic  stress  which  makes  up  this  field  or,  in  other 
words,  upon  the  strength  and  nature  of  the  electric  cur- 
rent. 

A  constant  uni-directional  current  will  create  a  mag- 
netic field  of  constant  polarity  and  of  uniform  tension. 
A  uni-directional  current,  but  of  varying  strength,  will  cre- 
ate a  corresponding  magnetic  field,  pulsating  or  varying  in 
intensity.  While  an  alternating  current  will  be  attended 
by  a  magnetic  field  alternating  in  polarity  with  a  frequency 
corresponding  to  the  alternations  of  the  electric  current 
and  of  an  intensity  varying  in  degree  with  the  strength  of 
that  current. 

We  have  found  that  the  most  noticeable  physiological 
response  to  an  electric  current  obtained  from  living  ani- 
mals is  that  resulting  from  sudden  and  wide  differences  of 


152  LABORATORY  MANUAL 

potential.  We  would  naturally  expect,  therefore,  that  a 
magnetic  field  with  rapidly  reversing  polarity  and  sudden 
variations  in  its  intensity  would  produce  more  noticeable 
results  in  a  living  organism  than  would  a  more  uniform  or 
constant  field. 

Careful  scientific  observation  and  record  of  the  rela- 
tion of  magnetic  stress  to  physiological  action,  either  in 
vegetable  or  -animal  structure,  separate  from  the  effects 
produced  by  the  passage  of  the  current  of  electricity  itself 
has  been  attempted  by  few.  What  has  been  done  so  far 
has  led  to  contradictory  conclusions.  Experiments  have 
for  sometime  been  carried  on  in  this  laboratory  with  the 
view  of  gaining  some  exact  knowledge  of  the  amount  of 
change  in  ordinary  life  processes  that  can  be  brought 
about  by  the  modifying  influences  of  various  forms  of 
magnetic  stress. 

These  experiments  were  commenced  more  than  two 
years  ago  in  this  laboratory  upon  man  and  growing  ani- 
mals by  subjecting  them  for  a  considerable  length  of  time 
to  the  influence  of  alternating  magnetic  fields. 

This  was  done  by  constructing  a  solenoid  three  feet 
in  diameter,  of  number  10  underwriters  wire,  and  with  a 
sufficient  number  of  turns  so  that  a  current  strength  of 
five  amperes  produced  an  average  of  sixty-five  C.G.S. 
lines  for  each  square  inch  of  space  in  a  plane  cross-sect- 
ing  the  space  within  the  coil.  Both  for  convenience  and 
to  determine  the  value  of  what  we  already  have  at  hand,  I 
used  the  current  from  a  Thompson  &  Houston  alternat- 
ing dynamo  employed  for  electric  lighting,  to  excite  the 
coil,  or  solenoid.  This  dynamo  makes  124  cycles  per 
second  or  248  alternations.  So  that  the  magnetic  field  or 
stress  in  the  space  enclosed  by  the  coil  changed  its  polar- 
ity with  this  frequency.  Whatever  occupied  this  space 


OF    ELECTROTHERAPEUTICS.  153 

therefore  was  subjected  to  this  rapidly  reversing  and  vary- 
ing magnetic  stress. 

The  first  series  of  experiments  was  made  with  the 
view  of  determining  the  influence  of  this  magnetic  field  on 
the  metabolism  of  tissue  as  determined  by  the  output  of 
urea.  Three  subjects  were  chosen.  Two  of  them  healthy 
young  men,  students  of  medicine,  and  the  other  a  man  of 
thirty-eight  years  of  age  who  had  for  two  years  been  suf- 
fering from  paralysis  agitans,  but  who,  aside  from  this 
nervous  affection,  was  in  fair  health.  The  diet  was  regu- 
lated in  amount  and  variety  in  each  case  for  a  week  pre- 
vious to  subjecting  them  to  the  magnetic  action,  and  a 
daily  estimate  was  made  of  the  amount  of  urea  excreted. 
Then  for  a  week's  time  without  change  of  diet  or  man- 
ner in  living  in  any  other  respect  each  one  of  the  three 
subjects  was  placed  within  the  solenoid,  comfortably  out- 
stretched upon  a  platform,  and  remained  there  for  two 
hours  each  day,  their  bodies  pervaded  by  the  alternating 
magnetic  stress  of  the  average  strength  above  mentioned. 
During  this  week  also  a  daily  estimate  of  the  quantity  of 
urea  was  made,  and  it  was  found  that  in  all  three  cases 
there  was  a  daily  increase  of  about  10  per  cent,  in  the 
amount  eliminated  during  the  period  in  which  the  subject 
was  in  the  magnetic  field.  No  other  effects  were  noticed 
that  could  be  detected  by  this  method  of  observation. 
There  was  no  apparent  change  in  the  depth  or  frequency  of 
respirations  nor  in  the  strength  nor  frequency  of  the  pulse 
or  arterial  tension;  though  it  is  possible  that  had  more 
delicate  or  exact  methods  of  testing  for  such  changes  than 
the  unaided  eye  and  touch  been  employed,  some  differ- 
ence in  these  functions  would  have  been  observed.  The 
subjects  were  conscious  of  no  change  in  sensation  or 
motive  power  except  that  the  patient  with  paralysis  agitans 


LABORATORY  MANUAL 


claimed  that  the  period  spent  within  the  coil  had  a  sooth- 
ing and  quieting  effect  upon  him  and  that  the  muscular 
tremor  which  attended  his  disease  was  for  several  hours 
after  each  exposure  much  less  violent. 

The  next  series  of  experiments  was  with  growing 
animals  to  determine  the  effect,  if  any,  of  the  alternating 
magnetic  stress  in  retarding  or  accelerating  their  growth. 
Experiments  of  this  nature  also  have  been  carried  on  at 
the  laboratory  almost  continuously  for  the  past  two  years. 

/     ^Itema-tint    current'     ?na,inf 

Q/  Ju/~i  t  c  h 

3  Tlmfiere     meter* 


Coils  enclosing     t/ie    an  i ma  fa 


Fig. 50. 

Some  of  the  time  the  animals  used  were  rabbits  and  at 
other  times  guinea  pigs.  As  soon  as  one  or  more  litters 
of  young  rabbits  or  guinea  pigs  were  old  enough 
to  be  separated  from  their  mothers,  they  were  di- 
vided into  two  bunches  as  nearly  alike  in  age  and  weight 
as  possible,  and  were  carefully  weighed.  The  two 
bunches  were  placed  in  conditions  of  living  in  all  re- 
spects similar  except  that  from  five  o'clock  in  the  evening 
until  midnight  one  bunch  was  placed  in  a  cage  (Fig.  50) 
made  of  the  kind  of  wire  above  mentioned  through  which 
an  alternating  five  ampere  current,  with  the  frequency  of 
alternations  above  mentioned  was  passing,  and  the  other 
bunch  was  placed  in  an  exactly  similar  coil  which  was  not 


OF    ELECTROTHERAPEUTICS.  •      155 

connected  with  the  current  circuit.  This  plan  was  pursued 
with  each  group  of  animals  selected  until  they  had  reached 
their  full  growth,  or  from  six  to  twelve  weeks,  according 
to  the  age  of  the  animals  at  the  commencement  of  the  ex- 
periment. The  laboratory  notes  contain  the  weekly  record 
of  the  weight  of  each  of  the  groups  of  animals  experi- 
mented upon  in  this  manner.  The  interesting  conclusion 
that  has  been  reached  so  far  from  these  experiments, 
which  are  still  in  progress,  is  that  the  group  of  animals 
immersed  in  the  alternating  magnetic  field  without  excep- 
tion began,  after  the  first  week,  to  outstrip  the  other  group 
in  weight,  and  a  gain  of  from  eighteen  to  twenty-four 
per  cent,  in  favor  of  the  animals  within  the  magnetic 
field  was  observed  each  succeeding  week  until  they  neared 
the  period  of  full  development,  at  which  time  the  weekly 
gain  was  less.  During  the  two  years  in  which  these  experi- 
ments have  been  going  on,  ten  separate  groups  of  animals 
have  been  used  either  in  the  magnetic  field  or  as  controls, 
each  group  containing  from  three  to  five  animals,  and 
uniformly  those  placed  in  the  magnetic  field  gave  evidence 
for  the  first  few  weeks  of  accelerated  nutritive  action.  In 
the  case  of  two  of  the  groups,  when  the  experiment  was  con- 
tinued beyond  eight  weeks,  the  curve  of  increase  shown  by 
the  magnetized  animals,  which  until  eight  weeks  ran  twenty 
per  cent,  higher  than  that  -of  the  other  group,  gradually 
declined  and  at  the  end  of  the  twelfth  week  their  weight 
had  fallen  a  little  below  that  of  the  other  group. 

It  is  an  interesting  fact  that  the  janitor  who  has  charge 
of  these  animals  and  is  a  shrewd  observer,  but  without 
knowledge  as  to  the  purpose  of  the  experiment,  called  our 
attention  to  the  fact  that  the  group  of  animals  that  was 
placed  within  the  magnetic  field  spent  much  more  time  in 
sleep  during  the  day  time,  that  is  when  the  current  was- 


1 56    '  LABORATORY  MANUAL 

withdrawn,  than  did  the  other  group,  but  in  no  other  re- 
spect except  the  increase  in  weight  did  he  nor  we  notice 
any  difference  in  their  appearance  or  conduct. 

As  far  as  these  experiments  go  they  appear  to  show 
that  alternating  magnetic  stress  is  in  some  way  related  to 
a  quickened  metabolism  of  tissue;  that  magnetic  energy 
goes  through  some  transformation  and  appears  as  physio- 
logical energy. 

These  results  are  very  similar  to  those  reported  by 
d'Arsonval  and  others  as  resulting  from  what  that  observer 
lias  termed  auto-conduction  brought  about  by  high-tension 
high  frequency  currents  and  as  the  apparatus  employed  by 
d'Arsonval  is  not  unlike  that  which  we  have  employed  in 
these  experiments,  although  the  description  of  d'ArsonvaPs 
experiments  was  not  published  until  some  months  after  we 
had  begun  those  we  have  been  describing,  it  is  not  improb- 
able the  effects  we  have  observed  are  due  to  the  same  cause. 
There  is  this  difference  to  be  noted,  however,  that  while 
the  currents  employed  by  d'Arsonval  were  of  the  high- 
potential  and  high-frequency  character,  the  current  em- 
ployed by  us  was  of  only  52  volt  pressure  and  the 
frequency  of  alternations  but  248  per  second. 


THE  THERMO-ELECTRIC  GENERATOR. 

(T.  419,  425.) 

In  1822  it  was  discovered  that  an  electric  current  could 
be  generated  by  heating  the  point  of  contact  of  two  dissim- 
ilar metals.  Later  it  was  found  that  if  a  number  of  points 
of  union  of  such  metals  were  so  arranged  that  alternate 
junctions  could  be  heated  the  E.  M. 
F.  would  be  increased.  This  is 
therefore  a  method  whereby  heat  is 
directly  transformed  into  electric 
energy  in  the  form  of  a  direct  cur- 
rent. The  accompanying  figure 
represents  a  thermo-electric  gener- 
ator employing  these  principles 
which  is  capable  of  producing  elec- 
tric currents  of  sufficient  strength 
and  intensity  for  various  practical 
applications.  The  heat  furnished 
by  the  combustion  of  gas  flowing  Fig.  51. 

from  an  ordinary  gas  burner  and  the  parts  other  than  the 
points  of  junction  of  the  dissimilar  metals  are  kept  cool  by 
allowing  a  stream  of  water  to  flow  through  the  apparatus. 
The  generator  tested  in  this  laboratory  has  an  E.  M.  F, 
of  6  volts  and  furnishes  a  current  somewhat  exceeding 
3  amperes.  The  output  of  energy  is  subject  to  very  slight 
variations.  The  following  are  some  of  the  therapeutic 
applications  to  which  such  a  source  of  electric  energy 
furnishing  a  current  of  this  nature  would  be  adapted: 


'58 


LABORATORY  MANUAL 


i.      It   would    heat    electric    cauteries    having    com- 
paratively    fine     wires,   or     would    light     some     of     the 

smaller    varieties     of    medical 
exploring  lamps. 

2.  It    could   be  used   to 
excite     a     medical     induction 
coil. 

3.  By  employing  a  good 
low  voltage    electric   motor  it 
could  be  used   to    run  various 
mechanical  devices  needed  in 
the  physician's  or  dentist's  of- 
fice. 

Owing  to  the  low  E.  M. 
F.  of  the  current  it  could  not 
be  conveyed  through  the  tissues  of  the  body  so  as  to  do 
effectively  any  of  the  work  which  we  have  discussed  under 
the  head  of  electrolysis,  phoresis,  or  the  physiological 
action  of  the  direct  current. 


ELECTRO-THERMIC  GENERATORS. 


We  have  considered  (p.  56)  electricity  as  a  source  of 
heat  for  heating  the  electro-cautery.  It  was  there  stated 
that  whenever  electricity  is  expended  in  overcoming  resist- 
ance it  reappears  in  the  form  of  heat  or  radiant  energy. 
Many  applications  of  this  principle  may  be  made  in  thera- 
peutics in  addition  to  that  of  the  electro-cautery. 

When  a  constant  source  of  electric  energy  is  conve- 
niently at  hand  as  is  the  case  in  many  hospitals  as  well  as 
in  private  houses  at  the  present  time,  a  steady  and  equable 
.application  of  heat  may  be  made  to  a  patient,  when  it  is 


OF    ELECTROTHERAPEUTICS. 


'59 


needed,    by  some    suitable   arrangement  for  transforming 
electric  energy  into  heat.     The  accompanying  figure  illus- 


Fig.  53. 

trates  one  of  these  in  the  form  of  a  pliable  and  adjustable 
pad.  It  consists  of  two  sheets  of  asbestos  with  wire  im- 
bedded in  them  enclosed  in  a  cover  of  flannel.  When  at- 
tached by  conducting  wire  cords  to  the  socket  of  an 
incandescent  lamp  the  temperature  of  the  pad  can  be 
raised  to  any  degree  desired  and  there  maintained  for  any 
length  of  time.  An  appliance  for  this  purpose  can  utilize 
either  an  alternating  or  direct  current. 


TABLE  OF  CONTENTS. 


Amalgamating  fluid, 21 

Amalgamation, 21 

Ampere,....  22,  23,  39 

Anaphoresis 51 

Anelectrotonus, 54 

Anions, 39 

Anode,  39 

Apostoli, 118 

Auto  conduction, 

Batteries,  body, 9 

"         notes  on, 20 

"         portable, 20 

Eattery,  experimental, 27 

"  .      storage, 63 

Bichromate  cell, 17 

"          solution, 10,  18 

Breeze,  electric  or  static, 

126,  133,  141 

Brush  discharge, 126 

Bunsen  cell, ... 16 

Calibration, 2,  3 

•Catalysis, 55 

Cataphoresis,  51 

Catelectrotonus, 54 

Cathions, 39 

Cathode, 39 

"         ray, 146 

Cautery,  Galvano, 56 

"         sources     of     current 

for, 59 

Cautery  transformer, 104 

Cell,  bichromate 17 

'      Bunsen,  16 

'      chloride  of  silver, 20 

'      Daniell, II,  15 

'      gravity, 15 

'      Leclanche,.... 18 

•C  harri  n, 117 

Chemical  reaction  of  cells, 14 

•Circuit, 14 

"       divided,  ...  34 

''       open, 14 

"      short, 14 


Coil,  induction, 73,  77 

''    physician's  induction,....      76 

"    primary, 77 

"    secondary,  82 

Combination  method  of  join- 
ing cells, 24,  26 

Controller,  current, 37,  38 

Crookes  tube, 73,  148,  150 

Cry ptoscope, 1 49 

Current, 7,  22 

"       density,  38 

"       direct, 85 

"       direction  of, 8 

"       galvanic, 85 

Current,     high-potential    and 
high-frequency,.. ..105,  113,  145 

Current,  induced, 86,  87 

''        magnetic  effects  of,..     64 

"        "second  order", 109 

"        sinusoidal, 91 

Current,  sinusoidal  physiolog- 
ical action  of, 95 

Daniell  cell, n,  15 

D'Arsonval,  

106,  113,  117,  119,  121 

Density  of  current, 38 

Direct  spark, 130,  140 

Disruptive  discharge  coil, 145 

Dubois — Raymond  coil, 83 

Edison,..  149 

Electric  belts, 9 

"       breeze, 126,  133,  141 

"       osmose, 51 

plasters 9 

Electrical  units, 22,  23 

Electrode,  directive, 135 

Electrolysis, 39 

''  rules  for,..  42 

Electrolyte,  39 

Electromotive-force 22 

Experimental  battery, 27 

Faradic    coil,    (see    induction 
coil) 80 


l62 


TABLE   OF  CONTENTS. 


Fluid,  battery, 18 

Fluorescent  screen, 143,  149 

Fluoroscope, 149 

Friction  spark, 134,  141 

Galvanic  coil, 4 

''         current, 85 

Galvano  cautery, 56 

Galvanometer,  2 

Generator,  thermo  electric,...  157 

Hertz, 112,  113 

High  potential  currents,  ...105,  113 
High  potential  currents,  ther- 
apeutics of n3 

High  tension,   high-frequency 

current, 145 

Holder,  plate, 5 

Holt/  machine,    T22,  123 

Impulsive  discharge, 106 

Indirect  spark, 133,  141 

Induction  coil, 73,  77 

"  current, 73 

Insulation,  positive, 140 

''  static,  I2Q 

In  terrupte  r , 80 

Ions, 39 

Kennelly  sinusoidal  machine,   100 

Leclanche  cell, 18 

Light,  electric, 62 

Local  action, 21 

Magnet,  temporary, 78 

Magnetic  effects  of  current,...  09 

"  field,  alternating, 151 

''  flux, 101 

Magnetism, 67 

Magnetism,  relation  to  living 

organism, I'5I,  152 

Magneto-electric  machine 90 

Magneto- motive  force,  101 

Mclntosh  sinusoidal  appa 

ratus 97 

Medical  induction  coil,... 74 

Milliampere, i 

Milliampere-meter,  physi 

cians, 3 

Morton,  Dr 13? 

Multiple  arc, 24 

Needle  spray, 13° 

Ohm, 22,  23 

Ohm's  law, 22 


Osmos,  electric, '51 

Phenol -phthalein, 45 

Physiological  effects  of  direct 

currents,  53 

Physiological    effects   of   high 

tension  currents, 113 

Physiological  effects  of  -sinu- 
soidal currents, 95 

Physiological  effects  of  static 

electricity,  128 

Plate,  collecting, 13 

"      generating, .  13 

Pole  changer, 34 

Poles, •  13 

Polarization,   batteiy, 10,  II 

"            effects  of,. 12 

'<            to  prevent, 12 

Primary  induced  current, 86 

Problems, 47,   48,  49,  50 

Rabbits,  experiments  with   in 

magnetic  fields,  153 

Reactions,  chemical,  of  cell's,  14 

Reluctance, .' TOI 

Resistance, 22 

body, 33 

internal, 32 

joint, 55 

laws  of, 46 

specific, 46 

unknown,  33 

Rheostat,  graphite, .  51 

Rhumkorff  coil, 144 

Rontgen  rays, 73,  142 

Rontgen  rays,  diagnosis  by,...  142 

"            "     generations  for,  143 

Rotary  transfoVmer, 65 

Salvioni,  149 

Screen,  fluorescent, 143 

Secondary  induced  current,...  87 

Sensitized  plates, 149 

Series, 24 

Shunt, 35 

"     current  controller,...  .  37.  38 

Sine  curve, 92 

Sinusoidal    apparatus,    Mcln- 
tosh,   97 

Sinusoidal     apparatus,     Ken- 
nelly   loo- 

Sinusoidal  current, 91 

Sinusoidal  current,  physiolog- 
ical and  therapeutic  uses  of.  95- 


TABLE  OF  CONTENTS. 


163 


Skiagraph, 145,  146 

Soldering, 9 

Spark,  direct, 130,  140 

"       friction...... 134,  141 

"•      indirect, 133,  141 

Spray 135 

Static    electricity,    physiolog- 
ical action  of, 128 

Static  induced  current,    

., 124,  136,  142 

Static  insulation  or  charge 129 

Static  machine, 121 

Storage  battery, 63 

Tesla,  Nikola, 106,  113 

Thermo  electric  generator, —    157 
Thermo-electric         generator, 

uses  of 158 

Thompson,  Elihu, 106,  113 

Topler, 122 


Toxines,  bacterial, 117 

Tubes,  vacuum, 146 

Tungstate  of  calcium, 149 

Unicellular  organisms,  ....;....   116 
Units,  electrical, 22,  23 

Vacuum, 147 

"         tubes, 146 

"             (l     action  in, 148 

Volt, 22,  23 

Volta  pile, 8 

Valtaic  cell, .  4 

Voltmeter, 8 

Wimshurst  machine, 122,  124 

X-rays, 142,   146 

"       experiments, 150 

Zinc,  chemically  pure, 6 

"    commercial, (> 


f\  LIST  OF  BOOKS 


PUBLISHED  BY 


PUBLISHER  AND  BOOKSELLER  TO  THE  UNIVERSITY  OF  MICHIGAN, 
ANN  ARBOR. 


Any  book  in  this  list  will  be  seat,  carriage  free,  to  any  address  in   the 
world  on  receipt  of  price  named. 

BO  WEN. — A  Teachers'*  Course  in  Physical  Training.  By  Wilbur  P. 
Bowen,  Director  of  Physical  Training,  Michigan  State  Normal  Col- 
lege. In  Press. 

CHEEVER. — Select  Methods  in  Inorganic  Quantitative  Analysis.  By 
Byron  W.  Cheever,  A.M.,  M.D.,  late  Acting  Professor  of  Metal- 
lurgy in  the  University  of  Michigan.  Revised  and  enlarged  by  Frank 
Clemes  Smith,  Professor  of  Geology,  Mining  and  Metallurgy  in  the 
State  School  of  Mines,  Rapid  City,  S.  D.  Parts  I.  and  II.  Third 
edition.  i2mo.  $1.75. 

The  first  part  of  this  book,  as  indicated  by  the  title,  consists  of  Laboratory  Notes 
for  a  Beginner's  Course  in  Quantitative  Analysis.  It  considers 'the  subjects  of 
Gravimetric  and  Volumetric  Analysis,  for  beginners,  by  means  of  the  chemical 
analysis  of  a  set  of  substances,  properly  numbered,  in  each  case  giving  the  methods 
to  be  followed  in  such  analysis;  also  the  methods  for  calculating;  and  preparing 
volumetric  standard  solutions,  generally  following  the  course  offered  by  Professor 
Cheever  to  his  students.  It  also  considers  the  methods  for  the  determination  of  the 
specific  gravities  of  various  liquids  and  solids. 

Although  a  number  of  the  analyses  contained  in  Part  I.  may  be  of  only  approxi- 
mate accuracy,  and  of  small  commercial  value,  such  are  yet  included  with  a  special 
purpose,  to  wit: — that  they  may  supply  the  student  with  a  wider  range  of  work  and  a 
greater  diversity  of  chemical  manipulation.  This  was  Professor  Cheever's  idea, 
and  it  is  certainly  a  good  one,  especially  since,  in  most  cases,  the  work  of  the  begin- 
ner simply  serves  to  emphasize  the  necessity  of  careful  scrutiny  of  details  and 
methods  for  practical  work  in  the  future. 

Part  J.  is  offered,  then,  for  the  use  of  schools  and  colleges,  and  it  is  intended  to 
supply  a  source  of  elementary  information  upon  the  subject  of  Quantitative  Chemi- 
cal Analysis  rarely  offered  in  such  form  in  works  upon  that  subject. — Preface. 

The  author  was  for  many  years  Professor  of  Metallurgy  in  the  University  of 
Michigan,  and  the  methods  here  presented  are  those  mostly  offered  by  him  to  his 
students.  As  a  beginner's  book  in  quantitative  analysis,  it  will  be  found  eminently  . 
practical,  and  it  can  be  honestly  recommended  to  the  student  who  desires  a  source 
of  elementary  information  upon  this  branch  of  applied  science.  The  book  is  divided 
into  two  parts,  the  first  consisting  of  laboratory  notes  for  beginners.  The  subjects 
of  gravimetric  and  volumetric  analysis  are  considered  by  means  of  the  chemical 
analysis  of  a  set  of  substances,  properly  numbered,  in  each  case  giving  the  methods 
to  be  followed  in  such  analysis,  and  also  the  methods  of  calculating  and  preparing 
volumetric  standard  solutions,  etc.  Methods  for  the  determination  of  specific 
gravities  of  various  liquids  and  solids  are  also  considered. 

Part  II.  contains  a  number  of  select  methods  in  inorganic  quantitative  analysis, 
such  as  the  analysis  of  limestone,  iron  ores,  manganese  ores,  steel,  the  analysis  of 


coal,  water,  mineral  phosphates,  smelling  ores,  lead  slags,  copper,  arsenic,  bismut  h, 
etc.     A  chapter  on  reagents  concludes  the  work. — Pharmaceuucnl  K>a. 

DEWEY.— 7^>  Study  of  Ethics.  A  Syllabus.  By  jonn  Dewey,  Pro- 
fessor of  Philosophy  in  the  University  of  Chicago.  Octavo.  144 
pages.  Cloth,  $1.25. 

D'OOGE. — Helps  to  the  Study  of  Classical  Mythology;  for  the  Lower 
Grades  and  Secondary  Schools.  By  B.  L.  D'Ooge,  Professor  in  the 
Michigan  State  Normal  College.  12  mo.  180  pages.  Cloth.  45  cents. 

A  bibliography  based  ou  practical  experience.  The  author  is  a  professor  in  the 
Michigan  State  Normal  College.  As  the  myths  of  all  nations  manifest  themselves 
first  in  religion,  secondly  in  art,  and  third  in  literature,  these  reading  references  are 
grouped  in  the  above  classes.  One  section  is  devoted  to  the  study  of  mythology  in 
the  grades,  and  an  introductory  chapter  gives  hints  for  teaching  the  subject  in  the 
lower  grades.  The  books  suggested  in  the  body  of  the  work  are  given  in  one  alpha- 
bet at  the  end,  with  publishers  and  prices;  there  are  also  blank  pages  for  additional 
references,  and  a  good  general  index.—  Publishers  Weekly, 

DOW. — Brief  Outlines  in  European  History.  A  Syllabus  for  the  Use  of 
Students  in  History,  Course  /.,  in  the  University  of  Michigan.  By 
Earl  Wilbur  Dow.  41  pages.  Pamphlet,  35  cents. 

DOW.—£rief  Outlines  in  European  History.  A  Syllables  for  the  Use  of 
Students  in  History,  Course  //.,  in  the  University  of  Michigan.  By 
Earl  Wilbur  Dow.  47  pages.  Pamphlet,  35  cents. 

DZIOBEK. — Mathematical  Theories  of  Planetary  Motions.  By  Dr. 
Otto  Dziobek,  Privatdocent  in  the  Royal  Technical  High  School  of 
Berlin,  Charlottenburg.  Translated  by  Mark  W.  Harrington,  for- 
merly Chief  of  the  United  States  Weather  Bureau,  and  Professor  of 
Astronomy  and  Director  of  the  Observatory  at  the  the  University  of 
Michigan,  President  of  the  University  of  Washington,  and  Wm.  J. 
Hussey,  Assistant  Professor  of  Astronomy  in  the  Leland  Stanford, 
Jr.  University.  8vo.  294  pages.  $3.50. 

The  determination  of  the  motions  of  the  heavenly  bodies  is  an  important  problem 
in  and  for  itself,  and  also  on  account  of  the  influence  it  has  exerted  on  the  develop- 
ment of  mathematics.  It  has  engaged  the  attention  of  the  greatest  mathematicians, 
and,  in  the  course  of  their  not  altogether  successful  attempts  to  solve  it,  they  have 
displayed  unsurpassed  ingenuity.  The  methods  devised  by  them  have  proved  use- 
ful, not  only  in  this  problem,  but  have  also  largely  determined  the  course  of  advance 
in  other  branches  of  mathematics.  Analytical  mechanics,  beginning  with  Newton, 
and  receiving  a  finished  clearness  from  Lagrange.  is  especially  indebted  to  this 
problem,  and  in  turn,  analytical  mechanics  has  been  so  suggestive  in  method  as  to 
determine  largely  both  the  direction  and  rapidity  of  the  advancement  of  mathemat- 
ical science. 

Hence,  when  it  is  desired  to  illustrate  the  abstract  theories  of  analytical  mechan- 
ics, the  profundity  of  the  mathematics  of  the  problem  of  the  motions  of  the 
heavenly  bodies,  its  powerful  influence  on  the  historical  development  of  this 
science,  and  finally  the  dignity  of  its  object,  all  point  to  it  as  most  suitable  for  this 
purpose. 

This  work  is  intended  not  merely  as  an  introduction  to  the  special  study  of 
astronomy,  but  rather  for  the  student  of  mathematics  who  desires  an  insight  into  the 
creations  of  his  masters  in  this  field.  The  lack  of  a  text-book,  giving,  within  mode- 
rate limits  and  in  a  strictly  scientific  manner,  the  principles  of  mathematical  astron- 
omy in  their  present  remarkably  simple  and  lucid  form,  is  undoubtedly  the  reason 
why  so  many  mathematicians  extend  their  knowledge  of  the  solar  system  but  Ihtle 
beyond  Kepler's  law.  The  author  has  endeavored  to  meet  this  need,  and  at  the 
same  time  to  produce  a  book  which  shall  be  so  near  the  present  state  of  the  science 
as  to  include  recent  investigations  and  to  indicate  unsettled  questions. 

FORD. —  The  Cranial  Nerves.  12  pairs.  By  C.  L.  Ford,  M.D.,  late 
Professor  of  Anatomy  and  Physiology  in  University  of  Michigan. 
Chart,  25  cents. 


FORD. — Classification  of  the  Most  Important  Muscles  of  the  Human 
Body,  With  Qrigin  Insertion,  Nervous  Supply  and  Principal  Action 
of  Each.  By  C.  L.  Ford,  M.D.,  late  Professor  of  Anatomy  and 
Physiology  in  the  University  of  Michigan.  Chart,  50  cents. 

FRANCOIS. — Les  Aventures  Du  Dernier  Abencerage  Par  Chateaubri- 
and, Edited  with  Notes  and  Vocabulary.  By  Victor  E.  Francois, 
Instructor  in  French  in  the  University  of  Michigan.  Pamphlet,  35 
cents. 

GRAY. —  Outline  of  Anatomy.  A  Guide  to  the  Dissection  of  the  Htiman 
Body,  Based  on  Gray's  Anatomy.  54  pages.  Boards,  60  cents. 

The  objects  of  the  outline  are  to  inform  the  students  what  structures  are  found 
in  each  region  and  where  the  description  of  each  structure  is  found  in  Gray's  Ana- 
tomy.—Thirteenth  ediiion,  dated  1897. 

GREENE.  —  The  Actiori  of  Materials  Under  Stress,  or  Structural  Me- 
chanics. With  examples  and  problems.  By  Charles  E.  Greene, 
A.M.,  M.E.,  Professor  of  Civil  Engineering  in  the  University  of 
Michigan.  Consulting  Engineer.  Octavo.  Cloth,  $3.00. 

CONTENTS. — Action  of  a  Piece  under  Direct  Force.  Materials.  Beams.  Tor- 
sion. Moments  of  Inertia.  Flexure  and  Deflection  of  Simple  Beams.  Restrained 
Beams:  Continuous  Beams.  Pieces  under  Tension.  Compression  Pieces:— Col- 
umns, Posts  and  Struts.  Safe  Working  Stresses.  Internal  Stress:  Change  of 
Form.  Rivets:  Pins.  Envelopes:  Boilers,  Pipes,  Dome.  Plate  Girder.  Earth 
Pressure:  Retaining  Wall :  Springs:  Plates.  Details  in  Wood  and  Iron. 

HERDMAN-NAGLER. — A  Laboratory  Manual  of  Electrotherapetitics. 
By  William  James  Herdman,  Ph.B.,  M.D.,  Professor  of  Diseases  of 
the  Nervous  System  and  Electrotherapeutics,  University  of  Michigan, 
and  Frank  W.  Nagler,  B.S.,  Instructor  in  Electrotherapeutics,  Uni- 
versity of  Michigan.  Octavo.  Cloth.  163  pages.  55  illustrations. 
$1.50. 

It  has  been  our  experience  that  the  knowledge  required  by  the  student  of  medi- 
cine concerning  electricity  and  its  relation  to  animal  economy  is  best  acquired  by 
the  laboratory  method.  By  that  method  of  instruction  each  principle  is  impressed 
upon  the  mind  through  several  separate  paths  of  the  sense  perception  and  a  manual 
dexterity  is  acquired  which  is  essential  to  success  in  the  therapeutic  applications. 

This  has  been  the  plan  adopted  for  teaching  electrotherapeutics  at  the  Univer- 
sity of  Michigan.  Every  form  of  electric  modality  that  has  any  distinctive  physio- 
logical or  therapeutical  effect  is  studied  in  the  laboratory  as  to  its  methods  of  gen- 
eration, control  and  application  to  the  pattent.  We  believe  this  to  be  the  only 
practicable  way  for  imparting  the  kind  of  instruction  required  for  the  practice  of 
electrotherapeutics,  but  in  our  attempt  to  develop  a  naturally  progressive  and  at  the 
same  time  complete  and  consistent  course  of  laboratory  instruction  we  have  found  it 
a  thing  of  slow  growth. 

This  laboratory  manual  is  the  final  result  of  our  various  trials  and  experiences, 
and  while  we  do  not  claim  for  it  either  perfection  in  the  arrangement  of  matter  or 
completeness  in  detail,  we  feel  that  the  time  has  come  for  putting  our  plans  in  a  form 
that  will  permit  for  it  a  wider  usefulness  as  well  as  gain  for  it  in  the  intelligent  criticism 
of  the  experienced  workers  to  the  field  which  it  seeks  to  cultivate. — From  Preface. 

HOWELL. — Directions  for  Laboratory.  Work  in  Physiology  for  the  Use 
of  Medical  Classes.  By  W.  H.  Howell,  Ph.D.,  M.D.,  Professor  of 
Physiology  and  Histology.  Pamphlet.  62  pages.  65  cents. 

HUBER.—  Directions  for  Work  in  the  Histological  Laboratory.  By  G. 
Carl  Huber,  M.D.,  Assistant  Professor  of  Histology  and  Embry- 
ology, University  of  Michigan.  Second  edition,  revised  and  enlarged. 
Octavo.  191  pages.  Cloth,  $1.50. 

It  is  adapted  for  classes  in  medical  schools  and  elsewhere  where  it  is  desired  to 
furnish  the  class  with  material  already  prepared  for  the  demonstration  of  structure 
rather  than  to  give  instruction  in  the  technique  of  the  laboratory  Provision  for  the 


latter  is  made,  however,  by  the  addition  of  a  section  of  about  50  pages  on  the  meth- 
ods for  laboratory  work.  This  section  includes  methods  of  macerating,  hardening 
and  fixing,  decalcifying,  impregnation,  injecting,  embedding,  chaining,  and  methods 
for  preparing  and  staining  blood  preparations.  The  last  is  accompanied  by  an  ex- 
cellent plate  of  blood  elements.  The  selection  of  methods  has  in  the  main  been 
judicious.  The  exposiiions  are  both  clear  and  concise. — Journal  of  Comparative 
Neurology. 

In  this  little  book  Dr.  Huber  has  given  us  a  model  manual  of  microscopical  tech- 
nique in  the  laboratory  study  of  histology.  The  subject  matter  is  divided  into  con- 
venient chapters,  commencing  with  the  cell  and  cell  division  (karyokinesis)  in  plant 
and  animal  life,  and  gradually  developing,  by  easy  stages,  the  most  complex  tissues 
of  the  animal  and  vegetable  organism.  Between  each  lesson  blank  pages  are  inter- 
leaved, to  be  used  by  the  student  for  drawing  the  objects  seen  by  him  with  a  pencil 
or  crayon — a  most  excellent  plan  as  nothing  fixes  the  appearance  and  characteristics 
of  objects  more  firmly  on  the  mind  than  drawing  them,  either  free-hand  or  with  a 
camera  lucida  (the  former  being  preferable,  as  it  educates  the  hand  and  eye).  With 
each  subject  is  given  the  source  and  origin,  the  best  methods  for  obtaining  and  pre- 
paring it,  and  attention  is  called  to  the  most  noteworthy  or  characteristic  points  for 
examination. 

The  second  part  of  the  book  is  devoted  to  methods  for  laboratory  work:  soften 
ing,  hardening,  decalcincation,  etc.,  of  the  matter  in  gross;  embedding,  sectioning, 
staining  and  mounting,  etc.  The  best  stains,  with  methods  of  preparing  the  same, 
and,  in  short,  a  general  formulary  for  the  various  reagents,  etc.,  concludes  the  work, 
which  is  intended,  as  stated,  as  an  aide  met  noire  supplementary  to  a  course  of  lec- 
tures on  histology. 

We  congratulate  Dr.  Huber  on  the  skill  with  which  he  has  developed  the  idea, 
and  the  didactic  methods  which  he  has  employed.  Such  a  book  cannot  but  prove  a 
great  help  to  both  student  and  teacher,  and  it  should  be  more  widely  known. — St. 
.Louis  Medical  and  Surgeon's  Journal. 

JOHNSON.—  Elements  of  the  Law  of  Negotiable  Contracts.     By   E.  F. 
Johnson,  B.S.,   LL.M.,   Professor  of  Law  in  the  Department  of  Law 
of  the  University  of    Michigan.     8vo.,   735  pages.      Full  law  sheep 
s        binding.     $3.75. 

Several  years  of  experience  as  an  instructor  has  taught  the  author  that  the  best 
method  of  impressing  a  principle  upon  the  mind  of  the  student  is  to  show  him  a  prac- 
tical application  of  it.  To  remember  abstract  propositions,  without  knowing  their 
application,  is  indeed  difficult  for  the  average  student.  But  when  the  primary  prin- 
ciple is  once  associated  in  his  mind  with  particular  facts  illustrating  its  applica- 
tion, it  is  more  easily  retained  and  more  rapidly  applied  to  analo  ous  cases. 

It  is  deemed  advisable  that  the  student  in  the  law  should  be  required,  during  his 
course,  to  master  in  connection  with  each  general  branch  of  the  law,  a  few  well-se- 
lected cases  which  are  illustrative  of  the  philosophy  of  that  subject.  To  ?  equire  each 
student  to  do  this  in  the  larger  law  schools  has  been  found  to  be  impracticable,  ow- 
ing to  a  lack  of  a  sufficient  number  of  copies  of  individual  cases.  The  only  solution 
of  this  difficulty  seems  to  be  to  place  in  the  hands  of  each  student  a  volume  contain- 
ing the  desired  cases.  In  the  table  of  cases  will  be  found  many  leading  cases  printed 
in  black  type.— From  Preface. 

LEVI-FRANCOIS. — A  French  Reader  for  Beginners,  -with  Notes  ana 
Vocabulary.  By  Moritz  Levi,  Assistant  Professor  of  French,  Univer- 
sity of  Michigan,  and  Victor  E.  Francois,  Instructor  in  French,  Uni- 
versity of  Michigan.  12  mo.  261  pages.  $1.00. 

This  reader  differs  from  its  numerous  predecessors  in  several  respects.  First, 
being  aware  that  students  and  teachers  in  the  French  as  well  as  in  the  German  de- 
partur-  nts  of  high  schools  and  colleges  are  becoming  tired  of  translating  over  and 
over  again  the  same  old  fairy  tales,  the  editors  have  avoided  them  and  selected  some 
interesting  and  easy  short  stories.  They  have  also  suppressed  thd  poetic  selections 
which  are  never  translated  in  the  class  room.  Finally,  they  have  exercised  the  great- 
est care  in  the  gradation  of  the  passages  chosen  and  in  the  preparation  of  the  vocab- 
ulary, every  French  word  being  followed  not  only  by  its  primitive  or  ordinary  mean- 
i"g,  but  also  by  the  different  English  equivalents  which  the  text  requires.  After 
careful  examination,  we  consider  this  reader  as  one  of  the  best  on  the  American 
maiket. 

LYMAN-HALL-GODDARD.—  Algebra.  By  Elmer  A.  Lyman,  A.B., 
Edwin  C.  Goddard,  Ph.B.,  and  Arthur  G.  Hall,  B.S.,  Instructor 
in  Mathematics,  University  of  Michigan.  Octavo,  75  pages.  Cloth, 
90  cents, 


MATTHEWS. — Syllabus  of  Lectures  on  Pharmacology  and  Therapeu- 
tics in  the  University  of  Michigan.  Arranged  Especially  for  the 
Use  of  the  Classes  Taking  the  Work  in  Pharmacology  and  Thera- 
peutics at  the  University  of  Michigan.  By  S.  A.  Matthews,  M.D., 
Assistant  in  Pharmacy  and  Thorapeutice,  University  of  Michigan. 
I2mo.  1 14  pages.  #1.00. 

MEADER. — Chronological  Otttline  of  Roman  Literature.  By  C.  L. 
Meader,  A.B.,  Instructor  in  Latin  in  University  of  Michigan. 
Chart,  25  cents. 

MICHIGAN  BOOK.—  The  U.  of  M.  Book.  A  Record  of  Student  Life 
and  Student  Organizations  in  the  University  of  Michigan.  Articles 
contributed  by  members  of  the  Faculty  and  by  prominent  Alumni. 
$1.50. 

MONTGOMERY-SMITH. — Laboratory  Manual  of  Elementary  Chem- 
istry. By  Jabez  Montgomery,  Ph.D.,  Professor  of  Natural  Science, 
Ann  Arbor  High  School,  and  Roy  B.  Smith,  Assistant  Profes- 
sor in  Chemical  Laboratory,  Ann  Arbor  High  School.  12  mo.  150 
pages.  Cloth,  $1.00. 

This  Work  is  intended  as  a  laboratory  guide  to  be  used  in  connection  with  a  good 
text-book  or  course  of  lectures,  and  in  its  arrangement  and  scope  it  is  based  upon 
the  practical  experience  of  two  instructors  in  the  Ann  Arbor  High  School.  It  i« 
therefore  restricted  to  such  work  as  may  be  done  by  the  average  high  school  pupil. 
The  experiments  which  are  directed  are  given  more  to  enable  the  student  to  compre- 
hend the  methods  of  analytical  chemistry  than  to  acquire  particular  proficiency  in 
the  work  of  chemical  analysis.  The  work  is  characterized  by  minuteness  of  explan- 
ation, a  feature  which  will  be  appreciated  by  the  beginner. — Pharmaceutical  hra. 

NETTO. — The  Theory  of  Substitutions  and  its  Application  to  Algebra. 
By  Dr.  Eugene  Netto,  Professor  of  Mathematics  in  the  University  of 
Giessen.  Revised  by  the  author  and  translated  with  his  permission, 
by  F.  N.  Cole,  Ph.D.,  formerly  Assistant  Professor  of  Mathematics 
in  the  University  of  Michigan,  Professor  of  Mathematics,  Columbia 
University.  8  vo.  301  pages.  Cloth.  $3.00. 

NOVY. — Laboratory  Work  in  Physiological  Chemistry.  By  Frederick  G. 
Novy,  Sc.D.,  M.D.,  Junior  Professor  of  Hygiene  and  Physiological 
Chemistry,  University  of  Michigan.  Second  edition,  revised  and 
enlarged.  With  frontispiece  and  24  illustrations.  Octavo.  Cloth, 
$2.00. 

This  book  is  designed  for  directing  laboratory  work  of  medical  students,  and  in 
showing  them  how  to  study  the  physics  and  physiology  of  the  digestive  functions  of 
the  blood,  the  urine  and  other  substances  which  the  body  contains  normally,  or 
which  it  speedily  eliminates  as  effete  material.  The  second  edition  has  appeared 
within  a  very  short  time  after  the  publication  of  the  first.  The  first  chapters  deal 
with  the  facts,  the  carbohydrates  and  proteids.  Then  follow  ethers  upon  the  saliva, 
the  gastric  juice,  the  pancreatic  secretion,  the  bile,  blood,  milk,  and  urine,  while  the 
closing  chapter  deals  with  a  list  of  reagents. 

While  the  book  is  manifestly  designed  for  the  use  of  Dr.  Novy's  own  students,  we 
doubt  not  that  other  teachers  will  find  it  a  valuable  aid  in  their  work.  At  the  close 
of  the  volume  are  a  number  of  illustrations  of  the  various  sedimentary  substances 
found  in  the  urine,  taken  from  the  work  of  von  Jaksch. — The  Therapeutic  Uazette 

This  book,  although  now  in  its  second  edition,  is  practically  unknown  to  British 
readers.  Up  to  the  present,  anyone  wishing  to  find  out  how  a  particular  analytical 
method  in  physiological  chemistry  ought  to  be  carried  out,  had  of  necessity  to  refer 
to  a  German  text-book.  This  comparatively  small  book — for  it  only  covers  some 
three  hundred  pages — gives  as  good  a  general  account  of  ordinary  laboratory  methods 
as  any  teacher  or  student  could  desire.  Although  the  author  refers  in  his  preface  to 
help  derived  from  the  works  of  Salkowski,  Hammarsten  and  others,  it  is  but  fair  to 
say  that  the  book  has  undoubtedly  been  written  by  one  who  has  worked  out  the 
methods  and  knows  the  importance  of  exact  practical  details  —  Edinburgh  Med, 
Jour.,  Scotland, 


Physiological  chemistry  is  one  of  the  most  important  studies  of  the  medical  curri- 
culum. The  cultivation  of  tnis  field  has  until  recently  been  possible  to  but  few. 
The  rapid  development  of  this  department  of  science  within  a  few  years  past  has 
thrown  much  and  needed  light  upon  physiological  processes.  It  is  from  this  quarter 
and  from  bacteriological  investigations  that  progress  must  chiefly  be  expected.  The 
rapid  growth  of  this  branch  of  chemistry  is  attended  by  another  result.  It  necessi- 
tates the  frequent  revision  of  text-books.  The  present  edition  of  Dr.  Novy's  valu- 
able book  is  almost  wholly  rewritten.  It  is  representative  of  the  present  state  of 
knowledge  and  is  replete  with  information  of  value  alike  to  student  and  practitioner. 
Few  are  better  prepared  to  write  such  a  book  than  Dr.  Novy,  who  has  himself  done 
much  original  work  in  this  field.— The  Medical  Bulletin,  Philadelphia. 

This  is  a  greatly  enlarged  edition  of  Dr.  Novy's  work  on  Physiological  Chemistry, 
and  contains  a  large  amount  of  new  material  not  found  in  the  former  edition.  It  is 
designed  as  a  text-book  and  guide  for  students  in  experimental  work  in  the  labora- 
tory, and  does  not  therefore  cover  the  same  ground  as  the  works  of  Gamgee,  Lea, 
and  other  authors  of  books  on  physiological  chemistry.  As  a  laboratory  guide  it 
should  be  adopted  by  our  medical  colleges  throughout  the  country,  because  it  is  an 
American  production,  contains  only  such  directions  and  descriptions  as  have  been 
verified  by  actual  practice  with  students,  and  because  it  is  clear,  concise  and  definite 
in  all  its  statements.  Its  first  ten  chapters  treat  of  fats,  carbohydrates,  proteins, 
saliva,  gastric  juice,  pancreatic  secretion,  bile,  blood,  milk,  a^d  urine.  Chapter  xi. 
is  devoted  to  the  quantitative  analysis  of  urine,  milk,  gastric  juice,  and  blood,  while 
chapter  xii.  gives  tables  for  examination  of  urine  and  a  list  of  reagents. — Am. 
Medico- Surgical  Bulletin,  N.  Y. 

NOVY. — Laboratory  Work  in  Bacteriology.  By  Frederick  G.  Novy,  Sc. 
I).,  M.D.,  Junior  Professor  of  Hygiene  and  Physiological  Chemistry, 
University  of  Michigan.  Second  edition,  entirely  rewritten  and 
enlarged,  563  pages.  Octavo.  $3.00. 

As  a  teacher  of  bacteriology,  the  author  has  had  extensive  experience,  and  the 
second  edition  of  his  book  will  be  highly  prized  by  students  for  its  practical  service 
and  thoroughness.  The  methods  of  investigation  described  are  mainly  those  which 
have  been  employed  in  the  hygienic  laboratory  or  the  University  of  Michigan,  and 
they  have  stood  the  test  of  practical  demonstration  and  usefulness.  One  of  the 
mo^t  interesting  parts  of  the  book  is  the  chapter  on  the  chemistry  of  bacteria,  and 
the  general  reader  cannot  fail  to  obtain  from  it  a  clear  understanding  of  the  com- 
plex changes  induced  by  these  minute  organisms.  The  functions  of  the  various 
ferments  are  also  very  cleverly  discussed.  An  enumeration  of  the  chapter  headings 
will  serve  to  show  the  scope  of  the  work:  Form  and  Classification  of  Bacteria;  Size 
and  Structure  of  Bacterial  Cell;  Life  History  of  Bacteria;  Environment  of  Bacteria; 
Chemistry  of  Bacteria;  the  Microscope;  Cultivation  of  Bacteria;  Non-Pathogenic 
Bacteria;  Bouillon,  Agar.  Milk  and  Modified  Media,  the  Incubator  and  Accessories; 
Relation  of  Bacteria  to  Disease — Methods  of  Infection  and  Examination;  Patho- 
genic Bacteria;  Yeasts.  Moulds  and  Streptotrices;  Examination  of  Water,  Soil  and 
Air;  Special  Methods  of  Work.  To  the  latter  subject,  two  chapters  are  devoted, 
in  which  are  very  fully  outlined  various  special  methods  of  value  to  advanced 
students.— Pharmaceutical  Era,  N.  Y. 

STRUMPELL.— 6/W/  Guide  for  the  Clinical  Examination  of  Patients. 
Compiled  for  the  Practical  Students  of  the  Clinic,  by  Professor  Dr. 
Adolf  Striimpell,  Director  of  the  Medical  Clinic  in  Erlangen.  Trans- 
lated by  permission  from  the  third  German  edition,  by  Jos.  L.  Abt. 
Cloth,  39  pages,  35  cents. 

PREFACE  TO  THE  SECOND  EDITION.— The  seccnd  edition  of  this  book  has  been 
improved  by  me  in  several  parts,  and  particularly  the  sections  treating  of  the  exam- 
ination of  the  stomach  and  nervous  system  nave  been  slightly  extended.  The  author 
trusts  that  the  book  may  also  fulfill  its  purpose  in  the  future,  in  assisting  the  student 
to  learn  a  systematic  examination  of  the  patient,  and  to  impress  on  him  the  most 
important  requisite  means  and  methods. 

SUNDERLAND. ^-(J;/^  Upward  Look  Each  Day.  Poems  of  Hope  and 
Faith.  Selected  by  J.  T.  Sunderland.  Third  Edition,  16  mo. 
White  Binding,  30  cents;  Cloth,  40  cents;  Full  morocco,  75  cents. 

SUN  D  E  R  L  AN  D  —  Grains  of  Gold.  Some  Thoughts  and  a  Brief  Prayer 
For  Each  Day  of  the  Monllis.  Designed  as  Daily  Helps  in  the 
Higher  Life.  Compiled  by  J.  T.  Sunderland.  White  Binding,  35 
cents, 


WARTHIN. — Practical  Pathology  for  Students  and  Physicians.  A 
Manual  of  Laboratory  and  Post-Mortem  Technic,  Designed  Espe- 
cially for  the  Use  of  Junior  and  Senior  Students  in  Pathology  at 
the  University  of  Michigan.  By  Aldred  Scott  Warthin,  Ph.D.,  M. 
D.,  Instructor  in  Pathology,  University  of  Michigan.  Octavo.  234 
pages.  Cloth.  $1.50. 

We  have  carefully  examined  this  book,  and  our  advice  to  every  student  and  prac- 
titioner of  medicine  is — buy  it.  You  will  never  regret  having  invested  your  money  in 
it,  and  you  will  acquire  such  a  large  fund  of  information  that  the  study  of  pathology 
will  become  a  pleasure  instead  of  the  drudgery  which  it  sc  unfortunately  seems  to 
be  in  many  cases. 

Part  I.  of  this  book,  embracing  some  103  pages,  deals  with  the  materials,  which 
includes  the  proper  examination  and  notation  of  the  gross  changes  which  have 
occurred  in  every  part  of  the  body.  In  fact  it  is  a  complete  expose  of  what  a  com- 
plete and  accurate  autopsy  should  be,  the  observance  of  which  is  oftener  followed 
in  the  breach  than  in  the  actuality.  Part  II.,  which  includes  134  pages,  deals  with 
the  treatment  of  the  material.  This  is  a  very  important  part  of  the  work,  as  it  gives 
explicit  directions  in  regard  to  the  instruments  to  use,  stains  and  staining  methods, 
drawing,  the  preservation  of  specimens,  Hardening  methods,  in  fact,  of  all  those 
technical  points  connected  with  practical  pathological  microscopy.  The  examina- 
tion of  fresh  specimens,  injections,  methods  fixing  specimens  as  well  as  special 
staining  methods  are  taken  up.  In  fact,  space  forbids  us  to  give  the  entire,  which 
are  most  valuable  in  every  detail.— St.  Loui*  Medical  and  Surgical  Journal. 

WATSON.—  Tables  for  the  Calculation  of  Simple  or  Compound  Interest 
and  Discount  and  the  Averaging  of  Accounts.  The  Values  of 
Annuities^  Leases,  Interest  in  Estates  and  the  Accumulations  and 
Values  of  Investments  at  Simple  or  Compound  Interest  for  all  Rates 
and  Periods;  also  Tables  for  the  Conversion  of  Securities  and  Value 
of  Stocks  and  Bonds.  With  full  Explanation  for  Use.  By  James 
C.  Watson,  Ph.D.,  LL.D.  Quarto.  Cloth,  $2.50. 

A  book  most  valuable  to  bankers,  brokers,  trustees,  guardians,  judges,  lawyers, 
accountants,  and  all  concerned  in  the  computation  of  interest,  the  division  and  set-" 
tlement  of  estates,  the  negotiation  of  securities,  or  the  borrowing  and  lending  of 
money,  is  the  above  work  of  the  late  Professor  James  C.  Watson,  formerly  Director 
of  the  Observatories  and  Professor  of  Astronomy  at  the  Universities  of  Michigan 
and  Wisconsin,  and  Actuary  of  the  Michigan  Mutual  Life  Insurance  Company. 

It  contains,  in  addition  to  the  usual  tables  for  the  calculation  of  simple  or  com- 
pound interest  and  discount,  many  tables  of  remarkable  value,  not  found  elsewhere, 
for  the  averaging  of  accoutns,  the  values  of  annuities,  leases,  interests  in  estates, 
and  the  accumulations  and  values  of  investments;  also  tables  for  the  conversion  of 
securities,  and  the  values  of  stocks  and  bonds. 

There  are  also  given  very  full  and  clear  explanations  of  the  principles  involved  in 
financial  transactions,  and  a  great  variety  of  miscellaneous  examples  are  worked 
out  in  detail  to  illustrate  the  problems  arising  in  interest,  discount,  partial  payments, 
averaging  of  accounts,  present  values,  annuities  of  different  kinds,  annual  payments 
for  a  future  expectation  (as  in  life  insurance),  or  for  a  sinking  fund,  conversion  of 
securities,  values  of  stocks  and  bonds,  and  life  interests. 

This  book  was  issued  from  the  press  under  the  author's  careful  supervision. 
Professor  Watson  was  noted  for  his  clear  insight  into  problems  involving  computa- 
tions, and  also  for  his  wonderful  ability  in  presenting  the  method  of  solution  of  such 
problems  in  a  plain  and  simple  manner.  The  varied  array  of  practical  examples 
given  in  connection  with  his  "  Table  "  shows  these  facts  in  a  remarkable  manner. 
This  book  provides,  for  those  least  expert  in  calculations,  the  means  of  avoiding 
mistakes  likely  to  occur ;  and  for  the  man  engrossed  in  the  cares  of  business,  the 
means  of  making  for  himself,  with  entire  accuracy,  the  calculation  which  he  may 
need,  at  the  moment  when  it  is  needed. 

WRENTMORE-GOULDING.  —  A  Text-Book  of  Elementary  Mechan- 
ical Drawing  for  Use  in  Office  or  School.  By  Clarence  G.  Wrent- 
more,  B.S.,  C.E.,  and  Herbert  J.  Goulding,  B.S.,  M.E.,  Instructors 
in  Descriptive  Geometry  and  Drawing  at  the  University  of  Michigan. 
Quarto.  109  pages  and  165  cuts.  $1.00. 

This  book  is  intended  for  a  beginners  course  in  Elementary  Mechanical  Drawing 
for  the  office  and  school.  Illustrations  have  not  been  spared,  and  the  explanations 
have  been  made  in  a  clear  and  concise  manner  for  the  purpose  of  bringing  the  stu- 


othe  desired  results  by  the  shortest  route  consistent  with  the  imparting  of  an 
accurate  knowledge  of  the  subject. 

The  first  chapter  is  devoted  to  Materials  and  Instruments;  the  second  chapter, 
Mechanical  Construction;  third  chapter,  Penciling.  Inking,  Tinting;  fourth  chap- 
ter, Linear  Perspective;  fifth  chapter,  Teeth  of  Grass. 

WRENTMORE. —Plain  Alphabets  for  Office  and  School.  Selected  by 
C.  G.  Wrentmore,  B.S.,  C.E.,  Instructor  in  Descriptive  Geometry 
and  'Drawing,  University  of  Michigan.  Oblong.  19  plates.  Half 
leather,  75  cents. 

Souvenir  of  the  University  of  Michigan,  Ann  Arbor.  Containing  38 
photo-gravures  of  President  James  B.  Angell,  prom.nent  University 
Buildings,  Fraternity  Houses,  Churches,  Views  of  Ann  Arbor,  Etc., 
Etc.  Done  up  in  blue  silk  cloth  binding.  Price,  50  cents,  postpaid. 

Physical  Laboratory  Note  Book. — A  Note  Book  for  the  Physical  Lab- 
oratory. Designed  to  be  used  in  connection  with  Chute's  Physical 
Laboratory  Manual.  Contains  full  directions  for  keeping  a  Physical 
Laboratory  Note  Book.  112  pages  of  excellent  writing  paper,  ruled 
in  cross  sections,  Metric  System,  size  7  x  9^  inches.  Bound  in  full 
canvass,  leather  corners.  Price,  by  mail,  30  cents.  Special  prices 
to  Schools  furnished  on  application. 

Botanical  Laboratory  Note  Book. — A  Note  Book  for  the  Botanical  Lab- 
oratory. Contains  directions  for  Botanical  Laboratory.  200  pages 
of  best  writing  paper,  ruled  with  top  margins.  Pocket  on  inside  of 
front  cover  for  drawing  cards.  Bound  in  substantial  cloth  cover  and 
leather  back.  Size  6x9^.  Price,  by  mail,  35  cents.  Special  prices 
to  schools  furnished  on  application. 


UNIVERSITY  OF  CALIFORNIA  LIBRARY, 
BERKELEY 

THIS  BOOK  IS  DUE  ON  THE  LAST  DATE 
STAMPED  BELOW 

Books  not  returned  on  time  are  subject  to  a  fine  of 
50c  per  volume  after  the  third  day  overdue,  increasing 
to  $1.00  per  volume  after  the  sixth  day.  Books  not  in 
demand  may  be  renewed  if  application  is  made  before 
expiration  of  loan  period. 


20w-l,'22 


BIOLOGY 

LIBRARY 

THE  UNIVERSITY  OF  CALIFORNIA  LIBRARY 


